Department no. 103 Hon. Lance A. Ito, Judge
APPEARANCES: (Appearances as heretofore noted.)
(Janet M. Moxham, CSR no. 4855, official reporter.)
(Christine M. Olson, CSR no. 2378, official reporter.)
(The following proceedings were held in open Court, out of the presence of the jury:)
THE COURT: All right. Good morning, counsel. Back on the record in the Simpson matter.
MR. SHAPIRO: Good morning, your Honor.
THE COURT: Mr. Simpson is again present before the Court with his counsel, Mr. Shapiro, Mr. Blasier, Mr. Scheck and Mr. Neufeld. Also present Mr. Uelmen. The People are represented by Mr. Clarke and Mr. Darden. The jury is not present. The record should reflect that this morning at eight o'clock the Court met with counsel informally for an hour this morning to review and discuss the various crime scene and autopsy photographs that the Prosecution wishes to offer into evidence. And that the Defense, at the request of the Court, will be filing a written response to the Prosecution's letter of April the 14th. That is to be filed by the close of business Friday, May the 12th, and that we will have the formal hearing as to each one of the photos the afternoon, May the 24th, at 4:00 P.M. All right. Mr. Neufeld, you indicated you had a matter you needed to take up before we resume with Dr. Cotton.
MR. NEUFELD: Yes, your Honor. Actually there are a few matters. As you may recall, we met twice already on the boards that the People intend to use today.
THE COURT: Yes.
MR. NEUFELD: And you were going to rule, one, on the objection to the use of the word "source." We believe that the proper term for that column should be "failed to exclude" and not "excluded by" because these are all, as even Dr. Cotton will testify or will testify, these are tests of exclusion and that is the standard terminology in the scientific literature, in the scientific community, so that is one of the issues that has to be resolved before the boards come out. I think you have already resolved, and I may be mistaken or the People consent to remove the "trail" word so that is no longer an issue. Then we have the issue of mixed stains and you had asked the People to first produce yesterday numbers on what the aggregate frequencies would be for the mixed stains. Umm, I'm told by Mr. Clarke that there is still--they don't have those numbers yet. But that obviously has to be resolved before the boards come out as well. Finally, your Honor, and perhaps most importantly, we talked about both in the interest of saving time and preserving a record that we would have standing objections before the various questions are posed to Dr. Cotton on issues which we had specifically objected to in Defendant's notice of objections to the testimony concerning DNA evidence and memorandum in support of this which was filed with the Court I believe on March 20, 1995. And the Court issued a written decision with respect to that motion. What we would like to do, obviously, is at this point--or get some guidance from the Court--is again incorporate this notice of objections by reference, and insofar as the witness, the witness' testimony, touches upon any of the issues which we have specifically raised in our notice of objections, that the Court will deem it that we object to that testimony and to the witness' answer, so we don't have to constantly interrupt the proceedings all along.
THE COURT: All right. Mr. Clarke, let's address the trail issue first. I take it you have consented to revise the board to "walkway and driveway"?
MR. CLARKE: Yes, that's fine, your Honor, and in fact those patches have been prepared or are being prepared.
THE COURT: All right. As to the concern about the nomenclature source, on the source versus not excluded, have you reevaluated your position on that?
MR. CLARKE: I think, as I mentioned to the Court last week, that it is our belief that, frankly, the term "possible source" is synonymous and neutral and there is no need to change it, but we do have patches if the Court so directs, however.
THE COURT: What patch do you have prepared?
MR. CLARKE: One that says "not excluded" for that particular column.
THE COURT: I will direct the use of the "not excluded" label. All right. As to the mixed stains issue?
MR. CLARKE: I think with regard to that issue we are going to have to require some more of the Court's time. This has taken some substantial mathematical calculations based on the samples that are involved, and I think an important background is as follows: With respect to this witness' testimony, there are only two particular samples that are involved. I don't know if the Court wants me to get into detail, but it is going to be our request that we actually convene a hearing with this Court about the issues that are involved in this, and they include, for instance, our position that this issue use has been totally waived by the waiver of a hearing. So I think we need some of the Court's time. I'm not going to get that far this morning, so however the Court would like to proceed with it, I think we need a more formalized hearing process.
THE COURT: All right. Refresh my recollection as to which mixed stain comes up in Dr. Cotton's testimony.
MR. CLARKE: There are two. One is item no. 78 from the bottom of Mr. Goldman's shoe that also has RFLP results. That one makes that one slightly unique in this series of results in this case as far mixtures. And the second item is the stain from the steering wheel of the Bronco that as I believe I mentioned to the Court last Friday, frankly, that stain is a little bit different than the others as well because while consistent with Mr. Simpson, there is obviously another contributor that is not directly related or may not be directly related to this case on the steering wheel, so that one is slightly different from the other mixtures as well. In this mixture issue, while I agree it needs to be resolved in some fashion before frequencies are discussed by Dr. Cotton, is frankly more relevant in the ensuing witness' testimony as well.
THE COURT: All right. Then I would suggest we take that up at one o'clock. Let's proceed with Dr. Cotton's testimony and we will get to the mixed stain issue at 1:00.
MR. CLARKE: Very good.
MR. SCHECK: One other brief--
THE COURT: I'm sorry. Let me ask Mr. Clarke one other question. Do you have any objection to the Court deeming the--allowing a standing objection as per the previous memorandum of points and authorities that was filed in late March?
MR. CLARKE: No, not with the--as long as it is with the understanding that we believe those objections have been waived previously as well, but as far as eliminating the need to object at every step, certainly that I think is an appropriate way of proceeding.
THE COURT: All right. Then I will deem these objections have been made for the course of the presentation of this witness. Mr. Scheck.
MR. NEUFELD: Obviously to the next--to the other DNA witnesses as well so we don't have to bring it up again.
THE COURT: Noted.
MR. SCHECK: Your Honor, after a lot of hard work, we have come up with a proposed instruction, preliminary instruction on DNA statistics, that is four short paragraphs, very short. I think balanced and a real candidate for Caljic. Isn't that what they call it here?
THE COURT: Yes.
MR. SCHECK: And I think it is one of the most important rulings you will make in the whole case and it is our best effort, very short.
THE COURT: All right. Do you have copies for opposing counsel?
MR. SCHECK: I have given Mr. Clarke a copy and maybe this is something that you would take up at one o'clock as well.
THE COURT: All right.
MR. SCHECK: I think it is-- (Brief pause.)
THE COURT: All right. Deputy Magnera, let's have the jury, please.
MR. CLARKE: I'm sorry, your Honor.
THE COURT: Mr. Clarke.
MR. CLARKE: Just one question. With respect to this witness' testimony, I understand there is available a wireless microphone, and when Dr. Cotton is, for instance, down in front of the jury, sometimes her voice is not being picked up by a microphone and I think it may aid her in being understood by the jury. With the Court's permission, we would like to use that.
THE COURT: If she is down off the witness stand then she is standing right before the jury box. Do you think it is really necessary?
MR. CLARKE: I think at times with these boards she is occasionally facing away, I think it will help, but I will leave that to the Court's discretion, obviously.
THE COURT: Where is Dr. Cotton? Dr. Cotton, are you familiar with the perils of using wireless microphones?
DR. COTTON: No, I don't think so.
THE COURT: Have you discussed this with her, Mr. Clarke?
MR. CLARKE: Only very briefly.
THE COURT: What is your feeling on that, Dr. Cotton?
DR. COTTON: I don't know what the perils are.
THE COURT: No. My point--how is your voice holding up?
DR. COTTON: Oh, it is fine. You know, we could wait until this afternoon and see if I'm having any problems.
THE COURT: The Court reporter seems to be voicing an opinion.
REPORTER OLSON: When her back is to me and she is facing the jury I do have difficulty understanding her.
THE COURT: Dr. Cotton, realizing there are no off-the-record comments while you are using the microphone--
DR. COTTON: I see.
THE COURT: All right. Let's use the microphone.
MS. PIETZ: Your Honor, I will need about five or ten minutes to set it up.
THE COURT: All right. Then we will proceed. Let's have the jury, please.
(Brief pause.)
(The following proceedings were held in open Court, in the presence of the jury:)
THE COURT: Thank you, ladies and gentlemen. Please be seated. And Dr. Cotton, would you resume the witness stand, please.
Robin Cotton, the witness on the stand at the time of the evening recess, resumed the stand and testified further as follows:
THE COURT: All right. Good morning again, Dr. Cotton?
DR. COTTON: Good morning.
THE COURT: You are reminded, ma'am, you are still under oath. And Mr. Clarke, you may continue with your direct examination.
MR. CLARKE: Thank you, your Honor. Good morning, ladies and gentlemen.
THE JURY: Good morning.
DIRECT EXAMINATION (RESUMED) BY MR. CLARKE
MR. CLARKE: Dr. Cotton, as far as these methods of DNA typing, and you have talked in broad terms about PCR and in more detail about RFLP, are these techniques simply a better way to type stains than for instance, ABO typing or conventional serology?
DR. COTTON: Yes, they generally will offer more information than conventional serology will offer.
MR. CLARKE: Again we spoke about RFLP or you spoke about RFLP typing yesterday. The second technology that you mentioned briefly yesterday I believe you referred to as PCR; is that right?
DR. COTTON: That's right.
MR. CLARKE: What year was that process discovered?
DR. COTTON: I believe that the first paper on PCR was published in 1985.
MR. CLARKE: As far as its use in forensics, is it newer or older than the RFLP typing process?
DR. COTTON: It is actually about--it came along at about the same time, although it was not being used quite as widely early on as the RFLP process.
MR. CLARKE: Are you familiar with who was the first scientist to use this PCR process in forensics?
DR. COTTON: Yes, I am.
MR. CLARKE: Who was that?
DR. COTTON: That would be Dr. Ed Blake.
MR. CLARKE: Do you know approximately when that forensic use of that technique occurred?
DR. COTTON: I only know that it was early, maybe 1986 or so.
MR. CLARKE: As far as this PCR process--and many of us, not all of us have heard of the movie Jurassic Park--what does PCR have to do with that?
MR. NEUFELD: Objection, your Honor. That is irrelevant.
THE COURT: Sustained.
MR. CLARKE: PCR does what? Can you give us a very brief summary?
DR. COTTON: PCR is a way of saying I want to replicate a small section of DNA and it allows you to replicate a small section of DNA in a way that if you have a very small amount of starting material, you can go through sufficient number of replications so that by the end of the process you will have enough of this small section to then do some analysis on.
MR. CLARKE: What role does it play, for instance, in old samples? And let's first of all ask can this process be used on samples of DNA that are perhaps years or decades or centuries old?
DR. COTTON: It can and it is being used on those types of samples.
MR. CLARKE: What types of samples is that?
DR. COTTON: There are samples from, I don't know what the proper term would be, but very ancient, for example, bone samples that have had very short sections, copied using PCR to look at how genes have changed over time. That is, if you can have a sample from a human being who is several thousand years old and look at a particular sequence of the DNA, you might say, well, how does that sequence compare to the same sequence in--in modern human beings?
MR. CLARKE: Has PCR been used on ancient animals?
DR. COTTON: I don't really know. It may have been but I don't really know.
MR. CLARKE: As far as this PCR process, is it like RFLP in the sense that it is a testing method or is it something a little bit different?
DR. COTTON: PCR is simply the process that allows you to make a lot of copies of a particular section of DNA and then the rest of the analysis may have many different forms. That is, what you do now with your section of DNA that you've replicated many times may not be the same for every purpose or every question.
MR. CLARKE: Would it be correct then that PCR would be more like one step in a typing process when DNA is being typed?
DR. COTTON: Yes.
MR. CLARKE: What about your own knowledge of PCR? How did that come about?
DR. COTTON: Umm, I had been to several meetings where PCR was discussed. I had done some reading where PCR was discussed. My own hands-on experience came from visiting two different laboratories where they were actively doing PCR and learning from the staff in those laboratories how to do PCR, and these--both of these visits to other laboratories, one was two weeks and one was a week. I had an opportunity then to learn from the staff there to do it myself and then back--going back to cellmark to help the rest of the cellmark staff who also had--some of whom had also been out to get training, which was different than mine, to set up the PCR that we do there.
MR. CLARKE: Who were the individuals that you--I'm sorry--whose labs you visited to learn PCR?
DR. COTTON: I went to a laboratory at Houston that was Dr. Tom Caskey and I went to Dr. Alex Jeffries' lab in the UK.
MR. CLARKE: The same Dr. Jeffries that you described yesterday?
DR. COTTON: Yes.
MR. CLARKE: How about your own personal hands-on experience with PCR? Could you describe that, please.
DR. COTTON: Well, I had those three weeks and then I had some experience hands-on time doing the PCR reaction while I was--while we were in the process of doing validation studies to set up PCR in our laboratory, and a number of other people did, too. I don't--I am not doing the PCR tests now. The PCR tests are done by the regular staff.
MR. CLARKE: As far as this copying process, is there a term used to describe what you actually do in taking small segments of DNA and copying them over and over?
DR. COTTON: Yes. The term is amplification. So people will talk about I have amplified a certain section of DNA.
MR. CLARKE: This process--and I believe you said that this process of copying over and over is directed at short segments of DNA?
DR. COTTON: The segments that are used for forensic analysis are relatively short and I'm talking about perhaps a hundred, 200, up to 400 base pairs in length. That is a pretty--in DNA terms that is a pretty small piece.
MR. CLARKE: So you are not talking about copying over and over this entire segment of DNA that you described as containing what was it, six billion bases or so?
DR. COTTON: No. You are not copying the whole thing; you are just copying a particular section.
MR. CLARKE: With regard to this copying possess, would it help to use a chart or a pad so that you could draw what this amplification or copying process involves?
DR. COTTON: Sure.
MR. CLARKE: Your Honor, then with the Court's permission Mr. Fairtlough will I believe set up the drawing pad for the witness.
THE COURT: We will reassemble our drawing pad.
MR. CLARKE: Reassemble.
THE COURT: Yes.
(Brief pause.)
THE COURT: And Mr. Clarke, I noticed yesterday that you were using the dry erase type marker. Does that have a longevity to it, permanence to it?
MR. CLARKE: I hope it is not disappearing ink.
THE COURT: You will notice that is what you are using there is dry erase.
(Brief pause.)
MR. CLARKE: All right. Your Honor, may this diagram be marked as People's next in order, which I believe is 247?
THE COURT: 247.
(Peo's 247 for id = diagram)
MR. CLARKE: All right. Dr. Cotton, if you could step down from the witness stand, and what would be an appropriate label for this chart to aid you in describing this copying process or amplification?
DR. COTTON: We will just call it "amplification."
MR. CLARKE: Very good. If you could just write that at the top.
DR. COTTON: (Witness complies.)
MR. CLARKE: All right. Now, if you would go ahead and if you could describe for the jury, please, what is this copying process?
DR. COTTON: Okay. Keep in mind now that you are starting--you have a sample and you have extracted the DNA, so those steps are the same as or similar to the RFLP process, and so let's just say for simplicity purposes that we have a single chromosome's worth of DNA that I'm going to use as a reference point here. So we are going to put in the tube our starting DNA and we are going to put in the tube a supply of the four DNA components; A's, G's, T's and C's and we will also put in the tube an enzyme, this is a protein, and it is called a polymerase, and this polymerase is basically going to assemble the A's, T's, G's and C's, and we are going to put one more thing in, which is referred to as a primer, and that is a very small piece of single-stranded DNA, usually about 20 bases or so. It can be longer or shorter, but that is just an example. So that we now have the components to make more DNA. This is what we are going to use to make more. We need our starting material, we need the building blocks, we need something to put the building blocks together, which is the polymerase, and the primer serves as an anchor for that polymerase to hold on to.
MR. CLARKE: Let me stop you for just a moment, Dr. Cotton. With regard to this term "polymerase," is that the first word of PCR, the process itself?
DR. COTTON: Yes.
MR. CLARKE: What does it stand for again?
DR. COTTON: Polymerase is a protein which can assemble more DNA in this case.
MR. CLARKE: And what does PCR actually stand for, what are the words?
DR. COTTON: PCR stands for the polymerase chain reaction and basically you are going through a cycle of steps which is why it is referred to as a chain reaction. You are repeating a cycle of steps over and over and over again. And what we will do here is just show you what one or two cycles looks like.
MR. CLARKE: All right. Go ahead.
DR. COTTON: So the first thing we will do is heat this DNA back up to about 95 degrees, enough so the strands will separate.
MR. CLARKE: Again, that is Centigrade, not Fahrenheit?
DR. COTTON: Yes. And at that will point we will allow the short primers or anchor points to bind and this is--these primers are designed so that the sequence of DNA that they have to hook up to is known and so you have a single-stranded piece in the primer, binding to this now single-stranded starting material, and all the A's and T's and G's and C's are pairing up. And then the polymerase will come along and directed by the bases on your starting material will reassemble a second strand.
MR. SHAPIRO: Your Honor, there is a juror that wants to get your attention.
JUROR NO. 2179: I can't see.
THE COURT: All right. Mr. Clarke, we have a vision problem.
MR. CLARKE: Yes.
(Brief pause.)
MR. CLARKE: Your Honor, would it be possible to put the drawing pad here where the podium is?
THE COURT: Let's put it there.
(Brief pause.)
THE COURT: Why don't you turn it as directly perpendicular as you can.
(Brief pause.)
THE COURT: Thank you.
MR. CLARKE: I'm not sure we have solved all the vision, though.
THE COURT: All right. Juror no. 1, can you see that?
JUROR NO. 230: I can see. That's fine.
THE COURT: Thank you, counsel. Proceed.
(Discussion held off the record between the Deputy District Attorneys.)
MR. CLARKE: Dr. Cotton, if you could, could you briefly describe again what you've already described and perhaps you can point to the various portions of the chart so that each of the jurors may see it.
DR. COTTON: Okay. We have double-stranded DNA starting material. We are going to heat the two strands, we'll just put a little "x" here on our starting material strands, drop the temperature down, allowing the primer to bind, the two primers to bind, and then allowing the polymerase to make a copy of this starting strand. So the polymerase is basically going along and says I have a t on my starting strand, I will put an a in. I have a C on my starting strand, I will put a g in. I also have a g on my starting strand, I have to put a C in, and so on. So now where we originally had a single strand to start out with, we now have two. Now, I'm--
MR. CLARKE: Go ahead.
DR. COTTON: --I'm sort of going to run out of a length of paper, but the idea is that you then start the process all over again, so you go--I have to stand on this side--so you go, start the cycle again, heat it up. These two double strands will come apart, these two double strands will come apart and now again you let--drop the temperature down and let the primers bind. And I have just made these shorter because there is not enough room. They wouldn't really be shorter, they would be the same length. And then allow the polymerase finish off making the copy for each one of those and so now we have four completed strands where we only started with one. So as you can see, each time you go through the cycle, you are going to double the number of strands that you started out with. If we start out with one, then we would go to two and then we go to four and the next cycle you would go to eight and so on.
MR. CLARKE: All right. Let me--perhaps you can stand on the other side so that I can ask you a question, a few questions about this process. You have used the term "primer." Does it act as something like a primer in priming a pump, for instance?
DR. COTTON: Well, it is not a bad analogy; it is not great. What it is, is the--the characteristics of the enzyme are such that it needs an end to start from. If you just separated the strands, it wouldn't have a place, it doesn't have an anchor point, so the primer is serving as an anchor point for the enzyme to then connect the next base to. It needs something in the way of the start of a second strand to actually connect, so the primers are in there both to say this is the section we want to copy. That is really what the primer does, is it identifies the section that you want to copy and then it starts as an anchor point for that enzyme to sit down and then move through and copy that piece of DNA.
MR. CLARKE: How do you know where the primer actually attaches to this segment of DNA?
DR. COTTON: You have designed your system, that is, you have to know up front the sequence of bases of the piece of DNA that you want to copy. There has to have been enough research done and development done so that--at least in the forensic setting here, you must know ahead of time the sequence of bases that exist in the piece that you want to copy. That has to be done ahead of time. Then you can manufacture in the lab the primers that have the sequence at the beginning and the end and then you are set to go.
(Discussion held off the record between the Deputy District Attorneys.)
MR. CLARKE: As far as these known sequences of where it starts, for instance, and you mentioned you have to know the sequence, have scientists looked at these areas to determine their sequences?
DR. COTTON: Yes. The development work for the genetic locations that are used for forensic testing with the PCR methodology, these regions have all been sequenced and a lot of other work, besides the sequencing, has been done to study these regions before applying that information to actually designing a forensic test.
MR. CLARKE: This copying process, first of all, do our bodies do that by themselves?
DR. COTTON: Not with this particular polymerase because this polymerase comes--is able to work at a very high temperature, but all our bodies have a similar enzyme so that when a cell replicates and divides to form two new cells, in the process of doing that you are replicating the DNA and the enzymes that perform that replication are also called polymerases.
MR. CLARKE: Would it be correct to say then that this PCR process simply does outside the body what the body does on its own?
DR. COTTON: Basically that is right.
MR. CLARKE: And it is as simple as that?
DR. COTTON: (No audible response.)
MR. CLARKE: In terms of this division in copying and so forth?
DR. COTTON: Yes.
MR. CLARKE: All right. Now, your Honor, if we could, I would like to put that drawing pad back where we had it yesterday and then continue on with some additional prepared charts.
THE COURT: All right.
MR. CLARKE: Perhaps you could have a seat again on the witness stand, Dr. Cotton, but probably not for too long.
DR. COTTON: (Witness complies.)
(Discussion held off the record between the Deputy District Attorneys.)
MR. CLARKE: Now, as far as this use of PCR, and I will step over here, Dr. Cotton, as far as this use of PCR in forensics, to your knowledge do we have some charts, prepared charts, that illustrate how you actually use this technique to type samples in forensic case work?
DR. COTTON: Yes. I have seen the chart that you are referring to.
MR. CLARKE: All right. Your Honor, at this time I would ask to be marked as People's next which I believe is--
THE COURT: 248.
MR. CLARKE: 248.
(Peo's 248 for id = chart)
(Discussion held off the record between Deputy District Attorney and Defense counsel.)
MR. CLARKE: Your Honor, for the record, this diagram can be labeled or can be described as "PCR analysis," and then showing at the top two large blocks, "step 1, extraction" and "step 2, amplification" and then a smaller block labeled "step 3, "detection."
THE COURT: Yes.
(Discussion held off the record between the Deputy District Attorneys.)
MR. CLARKE: All right. Dr. Cotton, with regard to this chart that has been placed on the board, have you had an opportunity to look at this before this morning?
DR. COTTON: Yes, I have.
MR. CLARKE: And with regard to this chart, does it illustrate various steps in the PCR-based typing process in forensics?
DR. COTTON: Yes, it does.
MR. CLARKE: Now, in particular--well, are there a number of steps that occur in this typing process?
DR. COTTON: Sure.
MR. CLARKE: In general terms are there fewer steps than in the RFLP typing process that you described yesterday?
DR. COTTON: Oh, there might be fewer. It sort of depends on how you count them.
MR. CLARKE: Okay. This board itself, and it is labeled at the stop "step 1, extraction." Can you describe what that refers to, and if there is a pointer there that would help you, please feel free to use it.
DR. COTTON: The top rectangle is simply illustrating that you have some kind of a stain and from that you do a DNA extraction and the DNA is going to end up basically in your test-tube and these tubes are actually very small. And then to that tube you will add, in addition to adding your DNA, you will add what is diagrammed up here as the PCR mix and the PCR mix is the DNA components, the A's, T's, G's and C's, the polymerase and the primers and some other salts or buffers, so all of those things go together in a single tube.
MR. CLARKE: All right. What happens at that point?
DR. COTTON: At that point you take that tube and put it in what's called a thermal cycler, it sort of looks like a cash register actually or a small one, but it has a metal block which is illustrated right here, (Indicating), and a computerized programmable method for controlling the temperature in that metal block, so the tube sits down very tightly. The holes in the block are simply the same shape as the tube so that when you put the tube down there, there is close contact between the tube and the walls of the metal block, and the temperature in the tube is then controlled by heating or cooling the metal block and you do this in a cyclical manner. And the cycle goes as we talked about a little while ago. You are heating the block up to 95, so the contents of the tube will be at 95, so you can denature the DNA, separate the strand, and the temperature is then dropped down. And I am not going to be able to remember what the exact temperatures are in the cycle, but the temperature is dropped down somewhere usually around 60 or 64 or 65 degrees, it could even be lower than that--anyway I don't remember right now--to allow the primers to bind and then the temperature is raised up to around seventy degrees to allow the enzyme to complete copying of the strand and then the cycle starts all over again. So you tell the machine in your programming what specific temperatures you want it to cycle through and how many cycles you want it to go through.
MR. CLARKE: In other words, this machine, you can program it or tell it basically how many of these cycles to go through, at what temperatures and so forth?
DR. COTTON: That's right, and how long each cycle is to be, like you are going to have it at 95 degrees for one minute and then you will drop it down to 55 degrees and stay there for thirty seconds and then you will raise it up to 70 degrees and you will stay there for, you know, fifty seconds or something like that.
MR. CLARKE: This heating and cooling process that you described, was PCR process used before there were machines that did this in a fairly automated fashion?
DR. COTTON: It was and my understanding was that when PCR was developed that basically the people were doing this by hand, that is, holding the tube in a water bath at a hundred degrees and then taking it out and putting it in another water bath at another temperature. So it would have been very tedious to do that. You would have a lot of researchers standing around taking up a lot of their time holding their tubes in water baths, so anyway, the computer age came and this machine was developed to essentially take care of that for you. So you put your tubes in, you set the machine up and turn it on and it goes through as many cycles as you have programmed it to do and then it holds your tube at a cool temperature until you come and retrieve it.
MR. CLARKE: Just briefly, there is a step 3 listed, that is called "detection." Is it your understanding that we will return to that in some detail in just a few moments?
DR. COTTON: Yes.
MR. CLARKE: All right. With regard to this amplification process, and in particular how these strands are copied, would it aid you to use a prepared diagram showing two different double helixes or ladders?
DR. COTTON: That only really relates to the kind of detection that we are doing.
MR. CLARKE: Very good.
DR. COTTON: So we could leave that for--
MR. CLARKE: As far as the detection itself?
DR. COTTON: Yes.
MR. CLARKE: Okay. Then if I could, I would like to return to the drawing pad. And Dr. Cotton, could you use the diagram and let's--let's add a new page if we could that I believe would be People's--
THE COURT: 249.
MR. CLARKE: 249.
(Peo's 249 for id = diagram)
MR. CLARKE: And with regard to this, if you could just illustrate and I would like you to actually write down a series of--just for illustrative purposes or examples--bases and how in this copying process how the primer would then act to add these bases that are floating around in this tube mixture. Do you understand what I'm asking?
DR. COTTON: I think so.
MR. CLARKE: Okay.
DR. COTTON: You want me to take a double strand, take it apart and show how the second strand is reconstructed?
MR. CLARKE: Correct. Just one cycle is fine.
DR. COTTON: Right.
MR. CLARKE: What would be an appropriate title to illustrate that point?
DR. COTTON: "more amplification."
MR. CLARKE: Okay.
THE COURT: I'm sorry, I couldn't hear the answer.
DR. COTTON: "more amplification." It is going to take me a minute to set this up.
MR. CLARKE: Very good.
(Brief pause.)
DR. COTTON: Okay. So I've made a very short sequence and I see there is a flaw in my thinking here, but we will sort of try to work past that. Double-stranded A's and T's, G's and C's nicely paired up and heated and create the two single strands. We are just unzipping the zipper. And now we want our primer to bind, so here is the flaw in my thinking. I'm going to have to make for a very short primer, because I didn't draw a very long sequence, so let's say we have put in a primer here, (Indicating), to have two T's and we put in a primer to fit the other side, which is going to be a t and a G. And you can see that this primer won't attach to this side and this primer won't attach to this side and the primers won't attach to each other, so you have to take these things into consideration and then you simply have your enzymes come along and the enzyme will come along and create this new strand. It will use this primer as its anchor point and now add--and remember we have got, you know, just individual A's, T's, G's and C's floating around here available to be put into the new DNA strands, so the primer will come along and correctly make a brand new strand on both sides.
MR. CLARKE: And what you--
DR. COTTON: I said primer but I meant polymerase. The polymerase will come along, hook onto this primer and correctly make--finish off here the new strand, (Indicating).
MR. CLARKE: So what you have illustrated is basically how this process works with the use of the primers and how from one strand you create two strands?
DR. COTTON: Yes.
MR. CLARKE: And then that process just continues through the cycles a number of times over and over that you described a few moments ago?
DR. COTTON: That's right.
MR. CLARKE: All right. Then Dr. Cotton, if you would, and what I'm going to ask you is with--
(Discussion held off the record between the Deputy District Attorneys.)
MR. CLARKE: Excuse me, your Honor. May I have a moment?
(Discussion held off the record between the Deputy District Attorneys.)
MR. CLARKE: Just a couple more questions if I could, Dr. Cotton. With regard to this primer, it latches onto the other side of the DNA strand; is that right?
DR. COTTON: It will bind--there is no other side. This is a single strand now and this is a single strand at the point that you've heated it, so the primer is the first starting point to creating another side.
MR. CLARKE: And it is from the primer on up or down the ladder, as the case may be, that it then starts this process of adding these bases one at a time?
DR. COTTON: That's right.
MR. CLARKE: All right. Very good. With regard to--and now just referring very previously to the large chart, which I believe is People's exhibit 248, as far as this--and you have described the second step on this chart, "amplification"; is that right?
DR. COTTON: That's right.
MR. CLARKE: With regard to the third step, is that the final basic step in this process of PCR typing?
DR. COTTON: That's right. You are going to--now you have made lots of copies of your DNA and you want to look at it for purposes of forensic use. You will be copying sections of DNA that have some difference from person-to-person and now you want to figure out, well, what does that difference look at for the sample I just copied.
MR. CLARKE: In other words, you actually determine the types in a particular sample so you can determine what persons can be excluded or included as possible donors?
DR. COTTON: That's right.
MR. CLARKE: With regard to this detection possess, is it the same or different from what you are looking for using the RFLP method?
DR. COTTON: Depending on the genetic location that you have amplified, there is--one of the detection methods is similar to the RFLP. That is, you are simply looking at how long a piece of DNA is you amplified. You know you started at one end, but there is some variation in the length, and you may need to explain that a little bit more. But the other--the other type of test that is available does not have anything to do with length really, but has to do with a sequence difference, so that at a particular genetic location I might have one sequence, Mr. Clarke might have another, Mr. Goldman, might have another, and so could you look at the sequence differences.
MR. CLARKE: Do we have a board that will illustrate that difference as well?
DR. COTTON: Yes, we do.
MR. CLARKE: All right. Your Honor, I would ask that a prepared diagram be marked as--
THE COURT: People's 250.
MR. CLARKE: Thank you.
(Peo's 250 for id = diagram)
(Discussion held off the record between the Deputy District Attorneys.)
MR. CLARKE: Thank you. Your Honor, for the record, People's exhibit 250 could be described as labeled "DNA" with what appear to be two depictions of a ladder side-by-side, DNA ladder.
THE COURT: All right.
MR. CLARKE: Dr. Cotton, with regard to this exhibit, first of all, have you had an opportunity to see it before?
DR. COTTON: Yes.
MR. CLARKE: Would this exhibit help you describe the differences between these two methods of typing samples that you just made a brief reference to a moment ago?
DR. COTTON: Yes. It is--it is the good example for--and it--it is a point of discussion for what is a sequence difference.
MR. CLARKE: All right. Could you then use this diagram to discuss that?
DR. COTTON: Yes. What we have here is the same diagram basically that we were using yesterday do show what is a DNA molecule and here we just have two of them that are side-by-side. And if you just go, let's say, from the top to the bottom and on one you will see we have an a t pair at the top and the other there is an a t pair at the top and we come down to a GC pair and the second one also has a GC pair, but here in the middle the DNA molecule on the left has an at pair. The DNA molecule on the right as a GC pair, so-- and then if you go on down the remainder of the three base pairs here, they are alike and a GC, an at and another GC, so the only difference we have here is the fact that the third base pair down on one diagram is an at and on the other is a GC. This is a DNA sequence difference. This sequence difference can be detected because you can amplify both of these pieces of DNA and then use a detection method to allow you to--you match either these pieces or those pieces and you can figure out that you have two varieties basically in your sample. You have one molecule that has an at pair and another one that has a GC pair, and so in the PCR diagram that we were looking at a little while ago, when it got to the bottom and it says "detection," this--to amplify two pieces of DNA and then detect that they had a sequence difference is one type of detection that is used for forensic analysis.
MR. CLARKE: What is the other type of detection method that the board just named, very briefly?
DR. COTTON: The other type is looking at a length difference, which is very similar to what you are doing in RFLP. You are also looking at a length difference. But maybe we should go back to the piece of paper just very briefly.
MR. CLARKE: All right.
(Brief pause.)
MR. CLARKE: You are going to create a new diagram, Dr. Cotton?
DR. COTTON: Yes, I am.
MR. CLARKE: All right.
(Discussion held off the record between the Deputy District Attorneys.)
MR. CLARKE: Your Honor, for the record, the witness is labeling this as "PCR length difference."
THE COURT: All right. This will be 251.
(Peo's 251 for id = diagram)
DR. COTTON: What I'm going to do is go back very briefly to the same analogy or the same example that I used yesterday in terms of a repeat, so let's say we have the same C, A, t repeat and again I'm just using that because it is a very easy example, and I have two different DNA pieces here, and they--one has two repeats and the other has four. And again, if I can somehow identify the end of each of these pieces, I could look and see how long they were. For the RFLP test we defined the ends by having an enzyme come along and literally cut these sections out. You can use the PCR test to also look at the lengths and you can do that by designing your primers so they will come along and bind just outside the repeat. Now, we could go through and redraw all the amplifications, but if you think about if, we look at just one of the strands here, if our primers come along and copy this section and copy this section, (Indicating), ultimately as you go through the PCR you will end up with a piece--many pieces that are this long, (Indicating). If you do the same thing with the other piece, with your primer sitting just outside the repeats, the pieces that are eventually going to become your product or your many pieces of DNA that you have now copied will include the full length of the primers and the four repeats that I have diagrammed, whereas over here we only had two. Now, instead of having a sequence difference like the board that we just talked about, now you have PCR product, but the difference is a length difference and you can analyze that length difference by separating the DNA strands to a gel. It doesn't always have to be exactly the same kind of gel that we talked about yesterday, but the principle is exactly the same and that is the DNA strands will move through the gel and separate out according to how long they are. And that is the other commonly used method of detection for looking at your PCR product, that is, looking at some kind of genetic difference in the DNA that you have now amplified.
MR. CLARKE: As far as the sequence differences, is my sequence difference at a particular set of markers different than yours?
DR. COTTON: It may be and it may be the same. Since we haven't tested both of us, I couldn't answer that question.
MR. CLARKE: What about in the area of these length differences?
DR. COTTON: The same thing. The variation in the population for these PCR markers is not extensive, so many of us may share some things and then some of us would be different, so whether or not you and I are different, I couldn't tell.
MR. CLARKE: And that is why--
DR. COTTON: It may be, but I don't know.
MR. CLARKE: Do you look at multiple genetic markers, more than one genetic marker, to get these differences if they exist?
DR. COTTON: You look at many genetic markers as you have the ability to look at, and no matter what kind of system you are using, be it PCR or RFLP, the more markers you look at, the more genetic locations you analyze, the more information you have. That is a generalization that will always be true for forensic testing. The more markers you look at, the more information you have.
MR. CLARKE: And is that your goal as a forensic scientist, to look for as much information as possible?
DR. COTTON: That would be the goal, yes.
MR. CLARKE: Do you have one more board to illustrate this PCR typing process?
DR. COTTON: Yes, we--I think so.
MR. CLARKE: Your Honor, at this time I would ask be marked as People's next in order--
THE COURT: 251.
MR. CLARKE: --a final PCR chart.
(Discussion held off the record between the Deputy District Attorneys.)
THE COURT: I'm sorry, 252, 251 being the drawing.
(Peo's 252 for id = chart)
MR. CLARKE: Your Honor, this exhibit--252?
THE COURT: 252--
MR. CLARKE: Is also labeled "PCR analysis" but it has two small blocks at the top, "step 1, step 2" and then a large block, "step 3," for the record.
THE COURT: All right.
MR. CLARKE: Now, Dr. Cotton, with regard to this chart, People's exhibit 252, would this help you in describing how these actual differences, whether they are sequence differences or length differences, are determined by you as a forensic scientist?
DR. COTTON: Yes.
MR. CLARKE: All right. Then if you would, with this chart, then describe for the jury these differences in typing and how they work.
DR. COTTON: Okay. So step 1, we extracted the DNA. Step two, we amplified it, we used the thermal cycler, and like you saw on the previous diagram. And now based on whatever genetic location we amplified, we are going to use one of these two types of detection, and the first type that is illustrated, which is on the left, is called a dot-blot or sequence polymorphism. That is sequence polymorphism just meaning sequence difference. That is exactly what we looked at on the two DNA molecules just a few minutes ago. So the set-up is you have a nylon strip which has DNA bound to it in specific locations and that is illustrated right here, (Indicating). There is a plastic tray and the tray has like little wells in it, sort of, and the strips sit in the tray. Solution is added to those strips and your amplified DNA is added to those strips and the DNA that is spotted onto the strip will bind to whatever part of your amplified DNA that it matches up. And where the DNA binds to the strip, the strip is then processed through a series of reactions to give you a blue dot on the strip where your sample DNA bound and these blue dots are then interpreted to say you have--and this is a term we haven't used--when I talked about genetic differences, if you go back to just mother and father, if you have two differences. Those are referred to as an allele. An allele is simply a form of a gene so that, for example, the two sequence DNA differences that we showed just a few minutes ago, those could be called two alleles, or the term Mr. Clarke was using would be two types. So from the series of blue dots on the strip, you will read off the types or the alleles for that DNA sample that you just analyzed. Then you simply write those down and record those. The other method, which is diagrammed on the right--
MR. CLARKE: I'm sorry, let me stop you for a moment, Dr. Cotton.
DR. COTTON: Okay.
MR. CLARKE: Your Honor, I would ask that be marked as People's next in order what can be described as a tray containing various slots in it.
THE COURT: All right. 253, plastic tray.
(Discussion held off the record between Deputy District Attorney and Defense counsel.)
(Peo's 253 for id = plastic tray)
MR. CLARKE: Dr. Cotton, showing you what will be marked People's--I'm sorry, was that 253, your Honor?
THE COURT: 253.
MR. CLARKE: --what is that item you have in your hands?
DR. COTTON: The item is the typing tray. It is the tray that is illustrated in the top two pictures here. It is plastic. This tray has strips laid in the wells. The strips have not been processed, so there is no blue dots on them. And the tray has a clear plastic lid which I taped down so that I wouldn't lose it, and this is the typing tray that is used in the laboratory and examples of the strips that are used in the laboratory to go through this series of reactions of adding your amplified DNA and developing the blue dots on the strip and from those blue dots then you would read your types from those samples.
MR. CLARKE: Where did that tray actually come from, as well as--I'm sorry. Did you say there were strips inside the tray right now?
DR. COTTON: Yes, they are.
MR. CLARKE: Where did they both come from?
DR. COTTON: They came from my lab but they are manufactured by Perkin Elmer Cetus, I believe.
MR. CLARKE: Would that be a tray and strips then that you would have used in case work if it hadn't been brought to Court today?
DR. COTTON: Oh, sure.
MR. CLARKE: With regard to those strips--and they are currently laying in the bottom of the tray; is that right?
DR. COTTON: That's right.
MR. CLARKE: What else is put into that tray other than the strips?
DR. COTTON: Do you want to go through the series of things that goes in here?
MR. CLARKE: If you could, yes.
DR. COTTON: The strips go in first and a solution that has some salt in it goes in and your amplified DNA goes in and that is incubated in a water bath so the water bath is controlling the temperature. The water isn't coming over the tray, long enough for your amplified DNA to bind to the DNA dots that are on the nylon. Then a series of reagents or components are added which allow--well, first the extra DNA is washed off and then a series of reagents are added to allow the development on the strip of the blue dot from your DNA bound, so you go through adding your amplified DNA, pouring off any that didn't bind, adding in a series of reagents that you need to develop the blue dots, pouring that off and then allowing them to develop.
MR. CLARKE: And then finally do you see the appearance of these blue dots? As is illustrated, they're the bottom left-hand side of People's exhibit 252, the large diagram?
DR. COTTON: Yes.
MR. CLARKE: All right. Your Honor, at this point I would ask that this exhibit be allowed to be distributed to the jury.
THE COURT: The plastic stray?
MR. CLARKE: Yes.
THE COURT: All right. Dr. Cotton, would you hand that to juror no. 1, please.
(The exhibit was passed amongst the jury.)
THE COURT: All right. Mr. Clarke, would you collect 253 from Deputy Russell, please.
MR. CLARKE: Yes.
THE COURT: And may I see that.
(Brief pause.)
THE COURT: Thank you.
THE COURT: Doctor. Thank you. Mr. Clarke.
MR. CLARKE: Thank you, your Honor.
MR. CLARKE: Dr. Cotton, if you could, could you then turn to the right-hand side of People's exhibit 252. And does that describe a different detection method or typing method when you are looking at these length differences?
DR. COTTON: Yes, it does.
MR. CLARKE: First of all, at the top it seems to have some letters and numbers. What are those?
DR. COTTON: It reads "AMP-FLP D1s80 length polymorphism."
MR. CLARKE: What does that first term mean, AMP-FLP?
DR. COTTON: The "AMP-FLP" is sort of a shorthand version of saying amplified length polymorphism, "amp" referring to amplified, "f" is fragment, "l" is length, "p" is polymorphism. D1s80 is the--is the nomenclature for the genetic location that is currently used in forensic labs that has a length polymorphism.
MR. CLARKE: We will return to that later, but is d1s80 simply a way of describing a particular genetic marker?
DR. COTTON: It is just the name of the marker.
MR. CLARKE: Like PGM is the name of a particular protein marker?
DR. COTTON: Exactly. Exactly.
MR. CLARKE: All right. Go ahead.
DR. COTTON: Okay. So in this case you have amplified DNA. The pieces that you amplified may have different lengths and so you are using a gel, which is our green gel here with the red DNA on it, and the DNA is loaded into the gel. It is a slightly different type of gel than the one I described yesterday, but the principle of how the gel works is exactly the same, and the gel is subjected to electrophoresis and the current moves the DNA through the gel. It moves through based on its size. And in this case you don't have to use p-32, you don't have to do anything fancy after you have run the gel. You can simply use a stain and visualize where the DNA fragments are, so at the end you have a gel that is stained and you can actually see the DNA fragments directly. And then you can photograph that gel and you can compare the positions of DNA bands in the various samples that you have now analyzed.
MR. CLARKE: And that is comparison of the bands like that same process of comparing bands using the RFLP method?
DR. COTTON: It is.
MR. CLARKE: Now, with regard to this length difference and this typing method described on the right, is that again simply one of the means of typing a particular genetic marker following the use of this PCR copying possess?
DR. COTTON: That's right.
MR. CLARKE: As well as this dot-blot method used to look at differences between people, whether it is based on a sequence difference?
DR. COTTON: That's right. With--with the RFLP everything is--you are looking at is length. When you use PCR, you can use a test that looks at sequence differences that is illustrated on the left or you can use a test that looks at length differences and that is illustrated on the right.
MR. CLARKE: One more question, if I could, and particularly while you are up, Dr. Cotton, I would like to take you back to the current drawing, which I believe is People's exhibit 251 labeled "PCR length difference." With regard to that particular drawing, you described the use of these enzymes to cut the DNA at certain locations?
DR. COTTON: I simply made reference to that in that for PCR--scratch that. For RFLP, to define the ends, that is to define the length, you use an enzyme to cut that length out. For PCR, to define the length,--to define the ends, you are using the primers. That defines the end and then you are copying however many repeats happen to be in between. And whether you have a few repeats or a lot of repeats, that determines the length.
MR. CLARKE: And these primers, how do they know exactly where to start this process?
DR. COTTON: The primers don't really know anything, but they are simply a piece of DNA that is single-stranded and they are going in and--and binding with the piece of DNA in the reaction tube that matches them. That is why my short primer example wasn't very good, because to be very specific, the primers need to be longer and they are usually around 20 or possibly more bases.
MR. CLARKE: But for purposes of showing how this process works, that is why you used shorter lengths or shorter sequences?
DR. COTTON: Well, if we drew out all of number of bases we would be here all day.
MR. CLARKE: We would need a taller chart?
DR. COTTON: We would.
MR. CLARKE: Your Honor, it was my intent to clear the charts and enter a slightly different area.
THE COURT: All right. Proceed.
MR. CLARKE: All right.
(Brief pause.)
MR. CLARKE: Dr. Cotton, as far as the use of PCR in your laboratory, was there a time when you actually began using this technique in your actual case work?
DR. COTTON: Yes.
MR. CLARKE: When did that happen?
DR. COTTON: We started doing PCR in case work in about--let me think about this a minute. I believe it was about June of 1992.
MR. CLARKE: And you began using the RFLP process in case work when?
DR. COTTON: Umm, for forensic case work we began about early 1988.
MR. CLARKE: And how do you decide--if a sample or a case comes into your laboratory, how do you decide whether to use the RFLP technique or to use the PCR copying process followed by typing genetic markers that PCR looks at?
DR. COTTON: For our particular laboratory, that may be related to a lot of different things. Umm, for example, it may be that another lab has--had already done RFLP, but doesn't have the capability of doing PCR, so they might specifically be asking us to do PCR. More typically, we would get a piece of evidence in and we would have to make an assessment. Is this piece of evidence--does it have enough DNA and is the DNA in sufficiently good condition to do RFLP? And if so, then you would proceed with RFLP. If the DNA or the piece of evidence contains only a very small amount of DNA or the DNA is very degraded, then you would choose to go forward with PCR.
MR. CLARKE: That is what I was just going to ask next. Do they each have their own advantages, these two different approaches?
DR. COTTON: Yes.
MR. CLARKE: Can you describe that and can you start with RFLP?
DR. COTTON: For RFLP you need a larger amount of DNA and it needs to be in very good condition.
MR. CLARKE: Why is that?
DR. COTTON: Because the test--if you remember yesterday I was talking about lengths of DNA that were thousands of base pairs long. You are looking at--in our lab we are looking at a piece of DNA that is anywhere from about 1500 up to 12,000 base pairs, so your DNA has to be in good condition to even--it has to be much bigger than that as starting material or your test won't work, so it has to be in good shape and you have to have a fair amount of it. The RFLP test has the big advantage in that it is very discriminating from one person to the next. There is so much variation in the population that each time you look at another genetic locus or genetic location with RFLP, you are getting a lot of information. That is, you can discriminate one person from the next with a high level of discrimination. On the other hand, the PCR, the tests that are currently available doesn't have that level of discrimination. It is a much lower level of discrimination, sort of in the range or maybe somewhat better than a whole series of serological markers. However, the PCR can use DNA when you have a very small amount or it is in very poor condition or both.
MR. CLARKE: So in other words, in terms of the ability to tell many of us apart as human beings, in other words, a powerful test as far as this ability to again tell large populations apart, is the RFLP procedure then the more appropriate to be able to determine that type of information?
DR. COTTON: Absolutely. Then that would be the test of choice.
MR. CLARKE: As far as the PCR process itself--and let's talk about both techniques in terms of how long they take to obtain results. Are there any differences between the two?
DR. COTTON: There can be significant differences.
MR. CLARKE: Can you describe that, please.
DR. COTTON: If you brought a sample into the lab and you didn't have--say you didn't have anything else to do, every other case that you were working on was all finished and you simply went through the PCR process, you could have results easily by the end of the week, so it would be very fast. And that is assuming you have, you know, a moderate number of samples, say three or four of something. Easily you would be done in a few days. The same test with RFLP could easily take you three months.
MR. CLARKE: Why is that? Why does it take longer?
DR. COTTON: The length of the time it takes to do the RFLP test is pretty standard from the time you extract the DNA until you load it on the gel, but the exposure of the x-ray film to that nylon membrane, if you have a lot of DNA, it can be short, as short as a day, but if you have little DNA, it can be as long as two weeks. So it could be that for the RFLP test you took two weeks to look at one genetic location, then you took another two weeks to look at the second and another two weeks to look at the third and you can see that rapidly eats up a lot of time.
MR. CLARKE: So it is that exposure of creating this x-ray film that takes a great deal of time; is that right?
DR. COTTON: It can, yes.
MR. CLARKE: Are there differences in the time it may take to create this x-ray from a particular sample?
DR. COTTON: Yes, and the differences are basically related to how much DNA you have in your sample. If you think about a large amount of DNA and a small amount, on your nylon membrane, you add your p-32 DNA probe. If you have a lot of DNA there you can bind a lot of probe. If you only have a little DNA there, you can only bind a small amount of probe. It is the emissions, the radioactive emissions from that probe that expose the x-ray film, so if you have a lot of probe there you will get an exposure on your x-ray film quickly. If you only have a little bit of probe bound because you only had a little bit of DNA to start with, it takes a long time to get enough exposure to that x-ray film to actually see something.
MR. CLARKE: And again, if I can show you what was marked yesterday as People's exhibit 246, is that one of those x-ray films or autorads that can require this fairly lengthy period of time to develop?
DR. COTTON: Yes.
MR. CLARKE: Now, you have described a little bit about the use of genetic markers and you actually identified one of the particular markers and I believe it was d1s80; is that right?
DR. COTTON: That's right.
MR. CLARKE: Is that just simply science's way of designating markers to tell one from another?
DR. COTTON: Basically, yes.
MR. CLARKE: Is there any particular reason there is numbers and letters in it instead of just letters like PGM?
DR. COTTON: The DNA locations that do not code for--do not have information for a gene that we know of, are given letter designations. The "d" stands for DNA. The "1" is because that particular location is on chromosome 1 and the "s80"--I actually can't remember what that refers to--but that also has a specific reference. So--and they are called anonymous DNA pieces, that is, they are not a gene that we know about and they are just given these "D" designations, it is an international nomenclature, so that if I read a journal article and it has one of these probes, it might say D5S20 and that would tell me that that DNA location was on chromosome 5 and if I could remember what the S20 meant, it would tell me more than that.
MR. CLARKE: As far as these genes that you say have these descriptions like starting with a "d" and then a number of the chromosome and so on, you said that something about them was not known. What is that?
DR. COTTON: Most of the--in fact, as far as I know, all of these genetic locations that contain these repeats, these are not genes in the traditional sense. Biologically speaking, in the traditional sense, a gene is a piece of DNA that contains information that creates a protein that then can go out into the cell and has a function. We know that these repeated sequences are not genes in that sense. Scientists don't actually know what the function of these repeats are. That doesn't mean they don't have one; it just means we don't definitely know what it is.
MR. CLARKE: As far as forensic science, and in this process, do you have a process of deciding or selecting which genetic markers to look at for purposes of identifying people?
DR. COTTON: Yes. For all of the markers that are currently used, there has been a substantial development period. That is, of the markers that are available, people have gone in and done the kind of research to say how much variation is there in the population for this marker, how easy is this marker to use, how much development do we have to go through so that many laboratories could have access to this particular marker. So this kind of work is done in a development sort of stage and then a marker is collected because of its utility, its ease of use, its discrimination power and so on, to be then used in--in a wider setting with--where many labs have access to or they choose to use a particular marker.
MR. CLARKE: As a forensic scientist would you, for instance, normally be interested in looking at the cystic fibrosis gene for purposes of your work?
DR. COTTON: No.
MR. CLARKE: Why not?
DR. COTTON: Although there is a lot of variation in the cystic fibrosis gene, that variation isn't widespread enough in the population so that each time you used it you would expect to get very much information. It wouldn't be sufficiently informative for forensic science purposes to use it.
MR. CLARKE: So is it correct then that the genetic markers you are most interested in are those that show us differences between people and can be easily used and are able to be typed, for instance, in older samples?
DR. COTTON: That would be right.
MR. CLARKE: Now, let's go back to PCR itself. Does it have uses outside forensic science or is it just limited to work in an area such as yours like human identification?
DR. COTTON: PCR is sort of the next thing that came along after this southern blot that is used everywhere. The use of PCR in forensic science would be a very tiny fraction of its total utility to biological research.
MR. CLARKE: What are some of the uses of PCR outside forensics?
DR. COTTON: PCR is used in the same kind--in genetic analysis, in gene mapping and it is used in many basic research settings simply because it allows you to get a whole lot of DNA from a very small amount of starting material, and whenever you can Get--scientifically, whenever you can get a lot of something, it gives you the ability to study it, so if you want to look at a particular section of DNA, then to get a lot of it makes you work a lot easier.
MR. CLARKE: You raised the term or you used the term "genetic diagnosis." Is that determining whether an individual, for instance, either has a genetic disease or is I think you used the term a carrier?
DR. COTTON: Yes.
MR. CLARKE: What is a carrier, just briefly?
DR. COTTON: That is if a parent has a genetic disorder, then the parent can transmit that genetic disorder to his or her children and this is something that many parents want to be aware of before they start having children, and you know, so you might say shall I have--a family might decide will we have children or will we adopt children, because one or the other of the parent could be the carrier of a genetic problem.
MR. CLARKE: Is PCR used, for example, to counsel parents, as you have just described, about the likelihood of a child of theirs having a genetic disease?
DR. COTTON: Yes.
MR. CLARKE: Is PCR used in the area of plant genetics?
DR. COTTON: I'm sure it is. I'm not a good enough plant biologist to know any specific applications, but I have no doubt that it is being used.
MR. CLARKE: You used the term "gene mapping." Can you just tell us a little bit about that?
DR. COTTON: In terms of understanding human diseases and human genetics, one of the primary things that scientists need to do or want to understand is how are genes located relative to each other, what gene is on what chromosome, what genes reside close to. And so in the process of figuring this--answering these questions for a specific genes, PCR will be a very helpful technique.
MR. CLARKE: Is PCR used, for instance, in the identification of the remains of American war dead?
DR. COTTON: Yes.
THE COURT: All right. Ladies and gentlemen, we are going to use this point to take a brief Court reporter recess for the morning. Please remember all my admonitions to you. Don't discuss the case among yourselves, form any opinions about the case, conduct any deliberations until the matter has been submitted to you, or allow anybody to communicate with you. And we will resume at ten minutes until 11:00. All right. Dr. Cotton, you can step down.
(Recess.)
(The following proceedings were held in open Court, out of the presence of the jury:)
THE COURT: Back on the record in the Simpson matter. All parties are again present. Let's have the jury, please.
(The following proceedings were held in open Court, in the presence of the jury:)
THE COURT: Thank you, ladies and gentlemen. Please be seated. Dr. Cotton, would you resume the witness stand, please. And why don't you pull the microphone close to you there, please. And, Mr. Clarke, you may continue with your direct examination.
MR. CLARKE: Thank you, your Honor.
MR. CLARKE: Dr. Cotton, you've described a little bit about the use of these tests, whether RFLP or PCR, to exclude people or include people; is that right?
DR. COTTON: That's correct.
MR. CLARKE: Is there any difference between those two things, excluding someone or including someone?
DR. COTTON: Well, those are two different--entirely different things, but I don't--I'm not sure what you mean.
MR. CLARKE: All right. Well, first of all, in excluding a person, what does that mean once you've conducted the test?
DR. COTTON: You've saying that that person cannot be a contributor to the sample that you've tested.
MR. CLARKE: What about the opposite? What about including someone?
DR. COTTON: Including someone, you're saying that this person could be a contributor--contributor to the sample that you've tested.
MR. CLARKE: Is there--in terms of the use of these tests, are they capable and do they in fact serve both of those purposes?
DR. COTTON: Yes, they do.
MR. CLARKE: Now, as far as the use of PCR--and you've described the fact that there are genetic markers or various locations on this DNA molecule that you look at where people differ?
DR. COTTON: That's right.
MR. CLARKE: And you described a little bit about the selection process, the process whereby forensic science decides which markers to look at; is that right?
DR. COTTON: That's right.
MR. CLARKE: Are there specific genetic markers that you look at in your laboratory following PCR amplification?
DR. COTTON: Of course.
MR. CLARKE: Okay. Do they have names that describe them?
DR. COTTON: Yes, they do.
MR. CLARKE: Could you describe those for the jury, please?
DR. COTTON: To tell you the truth, so I don't make a mistake, if you want me to list those markers, how about if you hand me one of my notebooks so I can read off of that.
MR. CLARKE: Sure. Would that assist you in describing each one exactly?
DR. COTTON: I think it would, yes.
MR. CLARKE: First of all--
MR. CLARKE: I'm sorry.
THE COURT: Go ahead.
MR. CLARKE: First of all, Dr. Cotton, these what appear to be two binders, could you just tell us what they are?
DR. COTTON: The two binders have copies in them of our original case folder, and I have the original case folder in my briefcase, but these are easier to manipulate.
MR. CLARKE: In other words, those are easier for you to work with?
DR. COTTON: That's right.
MR. CLARKE: Actually, let me approach it slightly differently. Is there a marker that you examine using the PCR process called DQ-alpha?
DR. COTTON: Yes.
MR. CLARKE: What is DQ-alpha?
DR. COTTON: DQ-alpha is located on chromosome 6 and it is one of the human leukocyte antigen markers. These microphones are doing funny things.
MR. CLARKE: Okay.
THE COURT: Why don't you take it off, take off the wireless, hand it to me.
(The witness complies.)
THE COURT: Thank you.
MR. CLARKE: Now, you used a fairly large term, human leukocyte antigen?
DR. COTTON: That is the name, generic name of the set of genes for which DQ-alpha is one. They are surface--they code for proteins that are on the surface of cells, and DQ-alpha is one of these proteins that's been very well characterized, and the DNA that encodes this protein is also very well characterized.
MR. CLARKE: Dr. Cotton, could you pull that microphone just a little closer to you?
THE COURT: Did you disconnect the Court's microphone?
AUDIO PERSON: Yes, your Honor.
THE COURT: We'll take a recess. Fix it.
(Recess.)
(The following proceedings were held in open Court, out of the presence of the jury:)
THE COURT: All right. Let's have the jury, please. Give me a test on there.
DR. COTTON: How's this sound?
THE COURT: Perfect.
(The following proceedings were held in open Court, in the presence of the jury:)
THE COURT: Thank you, ladies and gentlemen. Please be seated. All right. Let the record reflect we've been rejoined by all the members of our jury. Ladies and gentlemen, I apologize to you for the short delay, but I think you need to hear what's going on. And let's proceed. Mr. Clarke.
MR. CLARKE: Thank you, your Honor.
MR. CLARKE: Dr. Cotton, I believe you were about to discuss this marker called DQ-alpha.
DR. COTTON: That's right.
MR. CLARKE: And is that one of the markers that you type samples at following the use of this PCR copying process?
DR. COTTON: Yes, we did.
MR. CLARKE: What can you tell us about DQ-alpha? How well does it tell people apart?
DR. COTTON: DQ-alpha has six alleles. That is, there's six different forms of this DQ-alpha gene. And with that many alleles or forms, you can generate 21 different types in people. That is, so you're not confused, you--we each have two forms of any genetic locus or any gene. One comes from mother, one comes from father. So you're looking at how many combinations of these six things would exist, and there are 21 different combinations of the six alleles for this gene, DQ-alpha.
MR. CLARKE: Is there a particular term used in science to describe what a person's type is when they have two forms of a particular genetic--added to a genetic marker?
DR. COTTON: Yes.
MR. CLARKE: What's that called?
DR. COTTON: I mean--I think you're talking about are the term homozygous and heterozygous.
MR. CLARKE: All right. Well, let's start with that first. What do those terms mean? Are they--are they important? Do we need to know those terms?
DR. COTTON: Do you need to know them? Well, I don't know if you need to know them. Probably you do. When you have inherited from both parents the same form of a gene, that is so both your copy that you got from your mother and the copy you got from your father are identical, then you would be said to be homozygous, homo meaning the same and zygous referring to a zygote, which is combination of egg and sperm. So if you have two forms--you will always have two forms of the gene. And if they happen to be the same--let's use a very easy example. If you got a gene for blood group a from your mother and you got a gene for blood group a from your father, you would have two genes. Both are for blood group A, and you would be homozygous for that a.
MR. CLARKE: All right. Is there also a term called "genotype"?
DR. COTTON: Genotype simply--it just means what types do you have. Do you have an a and an a or an a and an B. That's your genotype, AA or AB.
MR. CLARKE: As far as this marker, DQ-alpha is concerned, if everyone in the courtroom were tested, would each of us be one of these 21 different types or genotypes?
DR. COTTON: We would each be one of those 21 types.
MR. CLARKE: Does that mean because there are presumably more than--well, there are more than 21 people in this courtroom. Does that mean it's likely or necessarily true that at least two of us have the same genotype?
DR. COTTON: Well, probably for those genotypes or combinations of genes that are common, we'd find more than one person in the courtroom who had the same type.
MR. CLARKE: That was actually going to be my next question. As far as these types that we each have, are they distributed absolutely equally or not?
DR. COTTON: They're not.
MR. CLARKE: Why is that?
DR. COTTON: I don't think we can--first of all, I'm not sure I can answer that question. That may be an evolutionary answer, and I'm not that knowledgeable about the DQ-alpha gene. However, what I know is that the types are not distributed evenly. So some types are very rare, some types are relatively rare and some types are very common.
MR. CLARKE: We'll return to it later, but are there studies done to determine how common or how rare these individual types are?
DR. COTTON: There actually is a very large amount of work published on how common or rare particular DQ-alpha types are in many different racial or ethnic groups.
MR. CLARKE: Still, with this DQ-alpha marker, how do you know it's a good marker to use in forensics?
DR. COTTON: Well, if you use as your Judge the first criteria that you want something to be relatively variable, that is a marker that shows a lot of variation is more useful than a marker that doesn't show very much variation. So on that criteria, DQ-alpha is quite good because with six alleles giving you 21 different types, that's a fair amount of variation and it's going to have useful information. The test that has been designed for forensic use for DQ-alpha, which uses PCR, only amplifies a very short section of DNA. That means the test is going to work well on samples that are degraded; and so for that reason, it's also very good.
MR. CLARKE: Is it, for instance, more useful than the ABO blood grouping types that this jury has already heard about?
DR. COTTON: Yes, it would be.
MR. CLARKE: Why is it more useful?
DR. COTTON: It has more variation.
MR. CLARKE: In what way?
DR. COTTON: Well, with ABO blood groups, you have three choices of alleles. You can be an a--you can be A, you can be O or you can be B, and that gives you a combination of six different genotypes; that is, taking those three things two at a time. So that means one--each one of us will be one of those six types as opposed to DQ-alpha where each one of us would be one of these 21 types. So DQ-alpha is going to be able to distinguish us one from the other better than ABO.
MR. CLARKE: Incidentally, of the six types for ABO you've described, are they actually type--fewer than that that can be actually determined from testing?
DR. COTTON: With normal serology testing, you can't distinguish all those types. People are developing DNA tests in which you will be able to distinguish all of those types.
MR. CLARKE: All right. In addition to DQ-alpha, do you type other genetic markers following the use of PCR?
DR. COTTON: Yes.
MR. CLARKE: And are they collected--first of all, how many other markers do you type in the laboratory?
DR. COTTON: In our laboratory, we're typing--well, we're typing five other markers. Actually, recently, we've added three more, but they were not done here and we don't need to worry about those. So for purposes of this case, we typed five additional markers besides the DQ-alpha.
MR. CLARKE: Are those five markers collectively known by any term?
DR. COTTON: The five markers are collectively referred to as poly-marker or PM, and that's simply the name given to those--that's not a scientific name really. It's just the company who developed this test refers to it as PM, generally standing for poly-marker.
MR. CLARKE: And are there different ways of describing those five different markers that are part of the poly-marker system? In other words, are they labeled by a particular name?
DR. COTTON: Yes. The five genetic locations that are tested in this poly-marker system, each one has a specific name.
MR. CLARKE: And can you briefly describe what each of those five are in terms of their name?
DR. COTTON: Sure, but this is what I'm going to take out of my notebook here. So--
MR. CLARKE: All right.
THE COURT: All right. Mr. Neufeld, you want to see that?
MR. NEUFELD: Thank you.
DR. COTTON: I'm just going to read this section here.
(Discussion held off the record between Mr. Neufeld and the witness.)
DR. COTTON: That I can do too.
THE COURT: All right. Mr. Clarke, proceed.
MR. CLARKE: Yes. Thank you.
MR. CLARKE: Dr. Cotton, what are those five--five genetic markers?
DR. COTTON: Each one of them has a short abbreviation which stands for the longer name. If you just focus on the abbreviation, that's probably a lot easier. The five markers are LDLR standing for low density lipo protein receptor.
MR. CLARKE: Can we stick with LDLR?
DR. COTTON: You want me just to give the initials?
MR. CLARKE: That's fine.
DR. COTTON: Okay. The other is GYPA, the third is HBGG, the fourth is d7s8 and the fifth is GC.
MR. CLARKE: Now, of those five you just described, one of them had that notation of the letter "d" with a number; is that right?
DR. COTTON: That's right.
MR. CLARKE: Would that then be another one of those markers where its function in the body is unknown?
DR. COTTON: As far as I know, it is, yes.
MR. CLARKE: And then the other four were described by letters basically; is that right?
DR. COTTON: The other four are actually genes and they have--the letters are just an abbreviation for the name of the protein that's been very well described for that gene.
MR. CLARKE: Now, this set of five markers that are part of poly-marker, how do you know they're good to be used or appropriate to be used in forensic work?
DR. COTTON: Each one of these markers doesn't--does not have a lot of variation, but grouped together, it still is informative. And really, the answer to your question is, in addition to the theoretical idea of how informative is this marker, this test has been designed to be also useful specifically for forensic purposes. The sections of DNA that are amplified are small and the typing is on the dot blot strips that you saw in the tray a while ago. So it's a test that's easy to do in the laboratory and it works on a--and has been shown to work on a very wide variety of samples. So it's applicable to all kinds of samples that come in in terms of forensic casework.
MR. CLARKE: Incidentally, that tray with the strips that you identified and was shown to the jury, was that actually a poly-marker set of typing strips?
DR. COTTON: Yes. The strips that were in the tray when you looked at them have the five poly-marker loci. And if you were looking at the strip, you would see that there were letters on the top of each one, and it's the LDLR, GRPA, indicating the dots in that set of the--in that portion of the strip or for that particular genetic location.
THE COURT: All right. Referring to People's 253.
MR. CLARKE: Yes. Thank you, your Honor.
MR. CLARKE: Going back to DQ-alpha for a moment, how long has it been used in forensic casework?
DR. COTTON: I think since about 1986.
MR. CLARKE: Going forward then to the poly-marker genetic markers, when were they begun to be used in forensic casework?
DR. COTTON: We started using the poly-marker test in January of 1994. There probably are some other labs who were using it earlier than we do, but I don't know exactly how--it wouldn't have been a lot earlier. Somewhere maybe within a year or so before we did. So let's say it's been being--it's been used in forensic casework since approximately 1993.
MR. CLARKE: Is there some process that these genetic markers undergo before they're actually used in casework or did someone just discover a gene and start using it immediately?
DR. COTTON: There's actually a very--what usually ends up being a very long process of development of the marker and then what's referred to as validation. That is, if another laboratory uses a marker, that doesn't necessarily mean that I can just bring it into my lab and start using it. So each lab that uses a particular test generally goes through a set of experiments in their laboratory to make sure that in--in the hands of the people in that laboratory, the test functions as it's supposed to, it meets its specifications and that everybody that is using it understands what it is they're doing. So there's development of the marker, then there's validation of the marker, which may occur in many different labs, and then there's training the staff in a particular lab to use that--that marker.
MR. CLARKE: And do you ensure that that marker can be correctly typed in evidence type samples before you even begin casework use of them?
DR. COTTON: Of course.
MR. CLARKE: As far as these poly-markers--well, let's start with DQ-alpha. Is DQ-alpha a marker that's tested--and I think you said more than one laboratory uses the poly-marker system. What about the DQ-alpha system?
DR. COTTON: The same is true of the DQ-alpha system. It's used by many forensic laboratories around the country and really around the world.
MR. CLARKE: That was going to be my next question. To your knowledge, are the poly-marker and DQ-alpha genetic markers used worldwide?
DR. COTTON: They are.
MR. CLARKE: You touched a little bit about as far as the five poly-marker genetic markers, that their variation is not as great as DQ-alpha?
DR. COTTON: That's right.
MR. CLARKE: Without getting into each one individually, can you tell us briefly how much variation that each show?
DR. COTTON: The five locations that make up the poly-marker system, all of those five locations either have two or three alleles or forms and they're all--they--they all are designated a or B, and if they have three forms in the kit, they're designated A, B or C. So you can--for example, if you have a marker that has an a type and a B type, any given individual then could have two A's, they would be an AA, they could have two B's, they would be a bb or they could have an a and a B and they would be an AB. So if you have two alleles, the most number genotypes you can have is three.
MR. CLARKE: DQ-alpha and these poly-marker genetic markers, do they represent sequence differences or length differences as you described them earlier today?
DR. COTTON: These are all sequence differences.
MR. CLARKE: As far as the actual typing of these DQ-alpha and poly-marker genetic markers, do you actually conduct these tests from scratch in terms of materials and what you use to be able to type samples?
DR. COTTON: No.
MR. CLARKE: How do you do it?
DR. COTTON: These tests, the DQ-alpha and the poly-marker, come as a kit, which means, you're buying in a box all the things that you need or almost all the things you need to do the test. Actually, you'd end up making a few solutions in the laboratory. But the strips come in the kit, the chemicals that you need to do the reaction, to create the blue dots come in the kit, the tray comes--you have to buy the tray and the kit. I guess actually you buy them separately. And the PCR mix that contains the primers and the polymerase and the a', G's, T's and C's. All that comes in the kit. So you're just supplying some very simple to make solutions and using the kit to do the test.
MR. CLARKE: When you conduct the more powerful RFLP typing technique, do you use kits to do that?
DR. COTTON: No.
MR. CLARKE: Why is there a difference between the two approaches to DNA typing as far as kits are concerned?
DR. COTTON: Well, somebody took the time to make the kit for DQ-alpha and poly-marker and nobody has tried to market a kit for RFLP testing. I guess you could, but it would have an awful lot of components.
MR. CLARKE: Is there anything unusual about using kits to conduct testing?
DR. COTTON: Oh, no.
MR. CLARKE: Why do you use a kit?
DR. COTTON: Because it's there.
MR. CLARKE: Does it have--
DR. COTTON: It's a good test and it's available and it's had an enormous amount of work done on it. If it wasn't a good test, you wouldn't use it. If it wasn't available, obviously you couldn't use it. So the company that makes the kit has put a lot of work into it and it happens to be very, very good.
MR. CLARKE: All right. Turning your attention if I can to the last genetic marker that we will talk about, d1s80, does that represent a genetic marker that's typed based on length differences as opposed to sequence differences?
DR. COTTON: Yes.
MR. CLARKE: Was DNA--I'm sorry. Was d1s80 developed as a marker to be used for forensics or did it have some different origin?
DR. COTTON: As far as I know, it was--it wasn't discovered--I mean it was discovered, but then basically it was developed specifically for forensic use. I really don't know if there's any research use for d1s80 or not.
MR. CLARKE: Outside forensics?
DR. COTTON: Right.
MR. CLARKE: How are you familiar with this particular genetic marker?
DR. COTTON: We've run this marker in our lab. We're not currently using it in our routine casework, but we've run it in our lab, and I've also actually read a number of papers that had to do with d1s80 and heard a lot about it at various scientific meetings.
MR. CLARKE: Why don't you use it in your casework in the laboratory?
DR. COTTON: The reason we're not using it in our casework is not because it's not a good marker. It's a very practical reason; and that is, the kind of gel that the d1s80 is run on is not a kind of gel that we would run other markers on. And so essentially, we aren't using it because it's a fair amount of work to do it and you get one piece of information off, that is the d1s80 piece of information. There are some other markers out there that we chose to use instead. They're not quite as informative as d1s80, but I can do more of them at a time. And so it was a very practical decision that you would just make in the lab to say, "do we want to do test a or test b?" It has nothing to do with whether or not d1s80 is a good marker. It was just our choice to go with another type of marker.
MR. CLARKE: So there are practical considerations that go into each laboratory's decision of what markers they're going to test?
DR. COTTON: That's right. And because not every--not every laboratory that does casework has the same type of casework or the same casework demands. And so all of those things go into your decision about what markers you're going to be using.
MR. CLARKE: As far as your familiarity with this d1s80 marker, what type of variation does it show?
DR. COTTON: The d1s80 has over--at least 24 alleles. That is at least 24 forms. I don't--haven't calculated how many genotypes that could give you, but you can imagine 20--at least 24 things taken two at a time. You can have many, many, many combinations. So it's a very informative marker and it's--except for the gel system, which takes some pains to do, it's a very good one.
MR. CLARKE: All right. I would like to shift topics if we can and ask you, are you familiar with the term "contamination"?
DR. COTTON: Certainly.
MR. CLARKE: What does that term mean to you?
DR. COTTON: It means so many different things that maybe I should try to break them down in terms of what it means to me.
MR. CLARKE: All right.
DR. COTTON: If you think of a biological sample, say you take a blood sample from someone in sterile conditions, you have a very clean sterile sample. That's sort of the ultimate in a good--in terms of having a good sample. As soon as you take that sample out of a sterile condition and say you have a bloodstain on a piece of cloth and you could think about well, that bloodstain is no longer sterile and it could be, quote, contaminated by anything that's on that cloth. So that would sort of be a second or let's say a first level. Now, in terms of analyzing evidence from a crime scene, you're always getting things that are like that. You're never being presented with a sterile sample. So in terms of a crime scene, contamination would mean that the sample is as it--that is, in retrieving the sample, it is as it was deposited, that nothing's been added to that sample in the process of picking it up, taking it to the crime lab and so forth. And then you can also say, "well, I have my sample from the crime scene. It came to the crime lab in exactly the same condition that it was at the crime scene." And then clearly, you need to be concerned with whether or not in the process of working with that sample in the laboratory, are you introducing any contamination from any source in the laboratory. So you can't use it very well as a generic term. I mean, you could, but unless you specify what kind of contamination you're talking about, then it becomes very difficult to discuss because you can--you can break it down and you can have many different kinds of contamination, some of which are inherent in the fact that you have a piece of evidence and not a sterile blood sample and some of which are not inherent and that could occur along the way in how that sample is handled.
MR. CLARKE: As a forensic scientist, are you concerned about contamination?
DR. COTTON: Of course.
MR. CLARKE: Why?
DR. COTTON: The idea of analyzing a piece of evidence is that you learn something about that piece of evidence. You're not interested in learning about-- that is, if you contaminate that piece of evidence with--let's talk about, say, you contaminate a piece of evidence with some other biological sample or some DNA in the laboratory. You--that will then interfere with your being able to come to a valid conclusion about that piece of evidence. And so you would certainly prefer not to have anything interfere with coming to a valid conclusion about a specific piece of evidence.
MR. CLARKE: As far as this area of contamination--and you've described the two basic DNA typing approaches that you use, both RFLP and PCR--is your concern about contamination the same for both of those techniques or is it different?
DR. COTTON: It's different.
MR. CLARKE: Why?
DR. COTTON: The PCR test is much more sensitive. You can do a PCR test with a very minute amount of starting material. So you would be more concerned. It doesn't mean you're not concerned with contamination for RFLP, but you're going to be more concerned with contamination when you're dealing with doing a PCR test on a piece of evidence.
MR. CLARKE: Okay. Let's take RFLP to start with. What steps if any do you take to deal with the problem or the potential problem of contamination in that testing process?
DR. COTTON: Okay. And what I'm--my answer is going to then be what we're doing in the laboratory because we're simply receiving a piece of evidence from outside. That is, we're not collecting the evidence ourselves. In the laboratory, our work is done in a--it's called a biological safety cabinet, but basically it's a setup where you have a piece of glass and you have a working area and the air is circulated within that working area to both protect what you're working on and to protect yourself. So you have some containment in the area that you're working with these samples. In our laboratory, when a sample is moved from one tube to another, that is, the tube has a label, it has a case number label and a sample number label, when it's--and in the process of doing DNA extractions and doing this testing, there are points where you have to remove the sample from one tube and put it into another. That transfer--the labeling on the tubes is witness. That is, somebody is checking to make sure that if I'm transferring from a tube that's marked 02, then I'm transferring it--the second tube I have in my hand is also marked 02. The other main precaution is that we do the DNA extractions for evidence samples as opposed to known samples. That is, when I say known, I mean you have a standard sample from a known individual. Those extractions are not done out in--well, they're done in this hood, but they're not done at the same time. So the knowns and the evidence samples are not worked on for purposes of DNA extraction at the same time.
MR. CLARKE: So those are the primary steps undertaken with regard to the potential for contamination as far as RFLP typing is concerned?
DR. COTTON: That's right.
MR. CLARKE: What about PCR? Do you undertake any different steps or additional tests to deal with this potential problem?
DR. COTTON: There are many additional features of how you do a PCR test to deal with minimizing any problems with contamination.
MR. CLARKE: Could you describe those, and are there general categories that you can place them into as far as the steps that you take?
DR. COTTON: I'm not sure what you're asking.
MR. CLARKE: Well, what are--what are the steps you take to deal with this potential problem?
DR. COTTON: Okay. The--let me think about this a second so it comes out organized. The PCR--the DNA extractions for PCR are done in a separate location than the extractions for RFLP. Now, in our lab, it happens to be that there's a separate one of these biological safety cabinets that's only used for PCR extractions. And the reason for that is that if you're doing something--if you have enough DNA to work with RFLP, that's a fair amount of DNA compared to what you might have in a PCR sample. So we don't want to be handling the large quantities of DNA that you can--that you would have for RFLP in the same place with the same equipment that you're handling the very small amounts. So most laboratories will have a separate location to do DNA extractions when those DNA extractions are for PCR. And in our lab, it's a separate--one of these hoods. The sample is--and in addition to that, for example, in the hood, the pipette-man or the, you know, the piece of equipment you're using to add things to the sample and take things out of the sample are specified. That is, you have a pipette-man that's used only for DNA and you have a series of pipette-man's that are used for everything else, so that you're not interchanging the piece of equipment that you're using to handle the DNA. You are that concerned. And the tips that you're using for the pipette-man are these art tips that have a filter in them so that you can't get any part of your sample up into the pipette-man and, therefore, accidentally transfer it to the next thing that you work with.
MR. CLARKE: Now, I believe--did you talk about extraction--I'm sorry--extracting evidence?
DR. COTTON: Well, basically that's--everything I just said relates to the area where the DNA is extracted.
MR. CLARKE: All right. Extraction was the first basic phase of dealing with evidence for purposes of PCR typing; is that correct?
DR. COTTON: That's right.
MR. CLARKE: Earlier, you described the second major phase involves what's called amplification, this copying process.
DR. COTTON: That's right.
MR. CLARKE: Do you take any precautions or additional steps to again deal with the potential for contamination during this particular phase?
DR. COTTON: Yes.
MR. CLARKE: What are those?
DR. COTTON: Well, first--now that you've finished the extraction, you want to set--you're going to set up the amplification. That is, you go through that process where you have a tube, and in that tube, you put your DNA and you put all the things you need to do the PCR, the primers, the polymerase and so on. That set up is done in a second area, a very clean area, and it's--in our lab, it happens to be a very small room, but it could--it could be some other just separate location. So the set up of the PCR reaction is done away from where the DNA extraction is done. Once that reaction is set up, it's then carried to yet a third location where the thermal cycler is where the amplification takes place. Once it's gone into that area where the amplification takes place, it does not ever go back in the other direction.
MR. CLARKE: Why is that?
DR. COTTON: I think about--in terms of the PCR, you have started with a tiny amount of material, and now after the process of amplification, you've generated millions of copies of that tiny amount of material. The biggest contamination problem that can occur with PCR is transferring some of that amplified product back to where you're starting out with, because that amplified product will amplify really well if it gets into anything else. So the--it's not the only concern, but the biggest contamination concern is that you do not get any of that amplified product, which is now a lot of DNA, back into anything that you're ever starting out with. So the DNA samples go from the extraction area to the set-up area, to the area where the thermal cycler is and where you then do the analysis of the amplified product and they do not go back in the other direction.
MR. CLARKE: And that's to, again, avoid this problem of lots of DNA being mixed in or commingled with small amounts of DNA?
DR. COTTON: That's right.
MR. CLARKE: Now, as far as--and I believe you described the fact that evidence is not extracted at the same time as known samples or did you mention that?
DR. COTTON: I did mention that with regard to RFLP testing, and the same--that same general procedure. That is, you don't do the DNA extractions for evidence and knowns at the same time. That's just a general precaution we use in our laboratory, and it's applied to everything.
MR. CLARKE: So as far as RFLP typing, your primary steps to avoid contamination are extracting samples at a different time, that is knowns versus evidence; is that right?
DR. COTTON: That's right.
MR. CLARKE: As well as witnessing of labeling samples; is that correct?
DR. COTTON: That's right.
MR. CLARKE: And are those the two primary steps taken as far as RFLP testing is concerned?
DR. COTTON: That's right.
MR. CLARKE: When you turn to PCR, you utilize those same two precautions; is that right?
DR. COTTON: You utilize those same two precautions and the other long list of precautions that I just talked about.
MR. CLARKE: As far as this case--and you described a little bit about the amplification phase. Was it correct that evidence samples in this case were amplified or did it happen that they were amplified on a different date from known samples?
DR. COTTON: In this case, it happened that that's the way the testing was done. Not only were they, the DNA extractions, done at a different time, but the amplifications, that is putting the tubes in the thermal cycler and allowing the amplification to take place, that also was done at a different time for the knowns and the evidence samples. That's not necessarily the--the way every case is worked. It just happened to be the way this case was worked really based on when we received samples and when we did each one.
MR. CLARKE: Does that play any role in the potential for contamination at all?
DR. COTTON: Well, it certainly acts as a preventative measure.
MR. CLARKE: But it's not something that you deem to be routinely necessary?
DR. COTTON: That's right.
MR. CLARKE: As far as these precautions--and let's focus on PCR for the moment. The precautions that you've described that you use in the laboratory, are they unique to forensic science or are they used in other areas of science involving PCR?
DR. COTTON: They are definitely not unique to forensic science because every lab that's using PCR, no matter what the reason, is still doing the same thing. They're taking a small amount of DNA and making millions of copies of it. So any laboratory that uses PCR for any reason has got to be concerned with making sure this amplified DNA that they get at the end doesn't get transferred back to any--any place along from the start of the sample on forward.
MR. CLARKE: Are these measures taken, for instance, in laboratories diagnosing diseases?
DR. COTTON: Certainly.
MR. CLARKE: Or in research laboratories?
DR. COTTON: In research laboratories also.
MR. CLARKE: Or in laboratories conducting paternity case evaluations or testing?
DR. COTTON: Exactly. And I'm not--I'm not--I don't mean to imply that, for example, a research laboratory would take exactly the same precautions that we would. They may be slightly different. But no matter what the setting is for PCR, you have to be concerned about making sure amplified product doesn't get back to your starting point.
MR. CLARKE: I'm sorry. Could I have just a moment, your Honor?
(Discussion held off the record between the Deputy District Attorneys.)
MR. CLARKE: So in terms of these--and just in terms of summarizing, these precautions that you take for PCR, they include the way you handle evidence; is that right?
DR. COTTON: Yes.
MR. CLARKE: The way you extract evidence in terms of when it's done at a same or different time than known samples in a case?
DR. COTTON: Yes.
MR. CLARKE: It includes precautions taken with regard to instruments that you use?
DR. COTTON: Yes.
MR. CLARKE: As well as the direction of flow so to speak of a sample going in one direction only as you described and not backwards?
DR. COTTON: That's right.
MR. CLARKE: As well as--and incidentally, are there other steps taken that to your knowledge we'll discuss later as well in terms of dealing with the potential problems of contamination?
DR. COTTON: Yes.
MR. CLARKE: Now, I'd like to shift topics a little bit to specific forensic case samples that are encountered. And in particular, with regard to evidence, can evidence at, for instance, crime scenes be subjected to basically the environment and the elements in that environment?
DR. COTTON: I don't think it's a question of "can." I think it's a question of that's absolutely bound to happen.
MR. CLARKE: Okay. What types of things can happen, for instance, to a piece of evidence found outdoors?
DR. COTTON: Well, it's going to be exposed to whatever temperatures are outdoors, whatever lighting conditions. There may be a lot of sunlight on that day. Could get rained or snowed on. I mean, whatever--if it's outside, it's going to be exposed to whatever's going on outside from the time that it was left there until the time that it's picked up.
MR. CLARKE: Incidentally, would the same be true, for instance, of a soldier killed in battle, out in a battlefield?
DR. COTTON: I would presume so.
MR. CLARKE: Or dead animals?
DR. COTTON: Dead animals too.
MR. CLARKE: You've described a little bit about, for instance, heat. Would that represent one instance of an environmental effect or something that's possible that happens outside?
DR. COTTON: Sure.
MR. CLARKE: And would that include sunlight as well?
DR. COTTON: Yes.
MR. CLARKE: And I think you mentioned rain or perhaps--
DR. COTTON: Well, I mean, you said outside. So I said, well, it could get rained--I mean, in California, maybe not, but--
MR. CLARKE: Sometimes. Some seasons it does.
THE COURT: You would be surprised.
MR. CLARKE: How about humidity? Is that something else that happens?
DR. COTTON: Of course.
MR. CLARKE: Are there other types of influences that are out there outside?
DR. COTTON: Well, I think you've named the major ones.
MR. CLARKE: With respect to these influences or effects like heat, humidity, rain and so forth, what do they do to DNA? What's their effect on DNA?
DR. COTTON: Basically, all of those things over time will act to gradually degrade the DNA; that is, break it up. The generalization that--that most everybody is aware of is that dry and cold works to preserve DNA and warm and moist works more towards degrading DNA. That's just a generalization, but that's pretty much the case.
MR. CLARKE: We'll talk about storage of samples in just a few moments. But is there anything about these environmental effects, whether sunlight, humidity, rain, et cetera, that can actually change DNA from one type to another?
DR. COTTON: No.
MR. CLARKE: How do you know that?
DR. COTTON: Well, you know that at a relative--at a very basic level because these things will not change the DNA sequence. Light, heat all of these things will not result in changing the DNA sequence. If you think about the kinds of locations that we're testing, we're testing lengths of DNA. Suppose you're doing an RFLP test and we're using my DNA and I have a DNA fragment that's 5,000 base pairs long. Degradation of DNA is a random process. There's no method or no enzyme that can go in from an environmental perspective and say, we're going to take that 5,000 base pair piece and it will then be converted to a 3,000 base pair piece, just a nice clean thing, goes from 5,000 to 3,000. That isn't what happens. Degradation is random. So that 5,000 base pair piece as it degrades is going to be cut up in many different places. And so it just gradually gets smaller and in many different sizes. So there is no environmental force, there is no environmental effect that can work to simply change one type and make it become another. You may lose the type altogether. You may degrade the DNA so much that you can't type it. But you won't just change types from one to another. Doesn't happen.
MR. CLARKE: Let's talk a little bit about storage. And you mentioned briefly about drying and--I'm sorry--making a sample cold as being a means or a method to preserve DNA?
DR. COTTON: Yes.
MR. CLARKE: Can you describe a little bit more about that? Why is that the case?
DR. COTTON: Problem with moisture--with high temperature and high humidity is that that enables bacterial growth, and bacterial growth will result in the DNA becoming degraded. That's generally the problem with high temperatures and humidity. Dry conditions and very cold conditions inhibit any kind of bacterial growth. And so they tend to be very good for storage. And keep in mind, unless your sample is sterile, sterile meaning the presence of no bacteria whatsoever, then any moisture and any heat will promote bacterial growth and that bacterial growth will gradually degrade the sample.
MR. CLARKE: What if you don't, for example, refrigerate or freeze a particular sample of DNA? What happens?
DR. COTTON: Well, it sort of depends on what stage it's at. If you're just at the evidence stage where you have some stain on some piece of clothing or some other substrate, then you really will see different effects with moisture and heat. Once your DNA is extracted--and it's really very clean. You don't have bacteria in there anymore. They've been destroyed in the extraction process. You may have bacterial DNA, but you don't have living bacteria. They've been destroyed. And so once your sample of DNA is purified, it does store over time best if it's kept cold. It's usually stored at minus 70 or minus 20 degrees centigrade. But if you left it out on the bench top at room temperature, you could really leave it out there for a very long time before it would be useless.
MR. CLARKE: Your work in the laboratory includes the receipt of certain--paternity samples for paternity tests; is that right?
DR. COTTON: Yes. The laboratory's work does.
MR. CLARKE: How do you receive samples for paternity testing?
DR. COTTON: We receive samples for paternity testing usually by federal express, and they're usually drawn from the individuals that are going to be tested the day before, they're packed up in a Styrofoam container so they can't break, they're shipped at ambient temperature, whatever temperature the air is, and received by us usually about 24 hours later.
MR. CLARKE: And are these in the form of liquid blood in tubes?
DR. COTTON: Yes. They're usually liquid blood drawn into EDTA tubes.
MR. CLARKE: Are these shipped--now, you mentioned the term, they're stored at ambient temperature, whatever temperature the outside is?
DR. COTTON: Well, that is, when they're given to federal express. Federal express isn't putting them in a refrigerated vehicle. So they may be flown to us or come in a truck. But whatever temperatures happen to be in that truck or the plane or, you know, all the various things it's going into before it's delivered to us, that's the temperature they're at.
MR. CLARKE: Does that create any problems in your ability to type these samples?
DR. COTTON: No, it doesn't.
MR. CLARKE: What happens, for instance, with one of these liquid blood samples? Well, let me rephrase that. Do you in the course of testing even in your forensic casework, that is identification casework other than paternity, do you receive samples in a liquid blood form?
DR. COTTON: Sometimes.
MR. CLARKE: Are they maintained in any condition as far as refrigeration in terms of their shipment or what they're shipped in?
DR. COTTON: If we're receiving a liquid blood sample for a forensic case, it's usually shipped in the same manner. Occasionally it's hand-delivered. Mostly, it's sent by some kind of carrier like federal express.
MR. CLARKE: What can happen to these liquid blood samples? What do you see in your casework that can happen as far as the ability to type DNA?
DR. COTTON: Well, it makes a big difference. If we're talking about liquid blood samples drawn from a known living individual, they're usually drawn in the same way the paternity samples are shipped to us and they're just fine. There are other types of blood tubes that you can draw people's blood into that have other types of preservatives other than EDTA. Those other types of preservatives are not as good for maintaining the condition of DNA as EDTA is. That's absolutely the--that's the preferred way for us to have a blood sample.
MR. CLARKE: Go ahead.
DR. COTTON: Well, I was just going to say, if the blood sample's from someone who's died, then you would be more concerned to make sure that it had been cool--it had been stored properly and that it had been drawn in an EDTA tube.
MR. CLARKE: Is that because blood taken from dead bodies is subject to this degradation process in a much faster fashion or faster fashion than blood from a living individual?
DR. COTTON: Yes.
MR. CLARKE: If blood is degraded in a liquid form, whether it's from a sample from a Coroner's office or paternity sample or another sample that you received in liquid condition, is there anything about that degradation process that can change the types of the sample involved?
DR. COTTON: No.
MR. CLARKE: What happens when it degrades? Is it the same as happens to, for instance, a stain that you described maybe outdoors?
DR. COTTON: Yes. It's the same.
MR. CLARKE: Now, as far as other things that exist out in the outside or in the environment, are there any in particular that can create a problem in your being able to type the DNA in that sample itself?
DR. COTTON: Any sample that is sufficiently degraded can be so degraded that you can't type it by any of the typing methods that are currently available. And there's an exception to that. It's typing of what's called mitochondrial DNA, which is DNA that is not in the nucleus. And that is the absolute last resource. That is, if the sample is in such bad condition, you can't do anything else with it, you might be able to do mitochondrial DNA, and there not very many places that will do that, that have that capability.
MR. CLARKE: As far as what's out there so to speak in the outdoors, what about soil? Does it play any role in the ability to type DNA?
DR. COTTON: Samples that are retrieved from soil are very difficult to type. Frequently you do not get any result.
MR. CLARKE: Why is that?
DR. COTTON: Presumably, you have bacteria in the soil that are participating in degrading the DNA. However, I don't know of a definitive experiment that's shown specifically that it's bacteria. So I only can tell you because this is the common experience, it's in the literature and many labs have had this experiences, if they are taking a blood or semen stain from soil, their success rate with those samples is very, very low.
MR. CLARKE: What about leaves? Are leaves another item similar to soil?
DR. COTTON: Yeah. Leaves aren't good either.
MR. CLARKE: Would your answer as far as the reason why be the same as soil?
DR. COTTON: It would.
MR. CLARKE: Is there anything about the presence of soil or leaves that could change the types that are found in a particular DNA sample so that they would be typed differently from what the contributor of that DNA actually is?
DR. COTTON: No.
MR. CLARKE: As far as laboratory precautions that you take again--and we're--and let's focus, if we can, on PCR typing, the precautions that you described earlier--is it a danger, for instance, if someone's coughing around a sample? And let's refer to an analyst.
DR. COTTON: Okay. So what you're asking me is, if I have a piece of evidence and I'm going to do PCR analysis on it and somebody's coughing, could that present a problem?
MR. CLARKE: Exactly.
DR. COTTON: It's possible. It's not--I don't think it's real likely, but I can't tell you it's impossible.
MR. CLARKE: What about sneezing?
DR. COTTON: Well, if you make it generic and say if I as the analyst transfer any of my cells onto the sample, then I could create a problem with that sample. But you have to think how much material you're transferring to that sample relative to how much material is there in the sample already. So it's--there's not a very--there's not a black and white answer to that question and there may not be a simple answer to that question. I--there is an experiment in the literature where they actually tried to contaminate a sample by the way the sample was handled, and it didn't cause any problem. That doesn't mean that it would never cause a problem. So you do want to be concerned about it, but you shouldn't assume it will cause a problem absolutely every time something like that occurs.
MR. CLARKE: In particular, are you referring to a publication in the scientific literature directly addressing the potential for problems as a result of some of these items we just discussed?
DR. COTTON: Yes, I am.
MR. CLARKE: Who wrote that publication?
DR. COTTON: The authors on that publication are Kate Comey and Bruce Budowle from the FBI.
MR. CLARKE: Could you spell both those last names?
DR. COTTON: I think Comey is C-O-M-E-Y and Budowle is B-U-D-O-W-L-E.
MR. CLARKE: And did that publication specifically deal with this question of whether or not these various influences could affect the ability to correctly type DNA samples?
DR. COTTON: Yes, it did.
MR. CLARKE: What conclusions did they come to?
DR. COTTON: The conclusion that they came to was that careful routine handling--
MR. NEUFELD: I'm sorry, your Honor. I'll object to the conclusion that they came to.
THE COURT: Sustained. Hearsay.
MR. CLARKE: As far as your reading of that publication, did that lead you to render any conclusions in your own mind about the appropriate way to deal with samples that are obtained, for instance, at crime scenes?
DR. COTTON: It contributed to my thinking about that, yes.
MR. CLARKE: Did it corroborate what your opinion was before you had even read the publication?
DR. COTTON: Well, at the time that I read the publication was during the time we were just starting PCR. So it added to my thinking, which was sort of still being formulated.
MR. CLARKE: Incidentally, as far as a stain let's say at a crime scene, to your knowledge, is there any reliable method of determining how old that stain is?
DR. COTTON: Not to my knowledge.
MR. CLARKE: As far as these environmental influences--actually, let me rephrase that, if I may, your Honor. As far as these items that we discussed, touching--well, sneezing, coughing, et cetera, do you have a personal opinion about their impact on your ability to properly type DNA samples that have been subjected to PCR amplification?
DR. COTTON: Yes, I have an opinion.
MR. CLARKE: What's that?
MR. NEUFELD: Objection. Foundation.
THE COURT: Sustained.
MR. CLARKE: With regard to these various impacts--well, let me rephrase that if I can. As far as your own experience in the laboratory with testing samples--and I'm referring to evidence samples--has that included samples obtained from a variety or under a variety of different circumstances?
DR. COTTON: Of course.
MR. CLARKE: How long have you been engaged in that? How long have you been in the laboratory gaining this type of experience?
DR. COTTON: Well, when I--when you say "you," really we're referring to my whole lab staff. Since about--well, since before 1992. We did a lot of work. We did a lot of validation work before we actually began to use PCR in casework. So we have the experience from the validation work and from the casework.
MR. CLARKE: As far as in the laboratory--and I'm going to direct your attention in particular to sample handling; for instance, extraction, amplification and typing of DNA--have you examined the results from your casework since you've used PCR in your laboratory?
DR. COTTON: Yes.
MR. CLARKE: Do those results include certain steps to determine if in fact the process of using PCR and then typing it is leading to or is actually including foreign DNA being typed in samples? Is that question clear?
DR. COTTON: I think so. There is a--
MR. NEUFELD: Excuse me. I still have an objection both as to vagueness in the question and secondly, again, foundation because we don't know whether it's to samples that are coming in--
MS. CLARK: This is a speaking objection.
THE COURT: It is a speaking objection.
MR. NEUFELD: Sorry.
THE COURT: Overruled. Also, a comment by counsel not handling the witness. Mr. Clarke.
MR. CLARKE: Do you recall the question?
DR. COTTON: You want to start over?
MR. CLARKE: Sure. As far as this actual PCR typing process that's gone on in your laboratory, do you take steps to detect whether or not there may be DNA present that you're able to determine types from that didn't come from a particular evidence sample?
DR. COTTON: Yes.
MR. CLARKE: Does that involve the use of controls?
DR. COTTON: It does.
MR. CLARKE: What is a control?
DR. COTTON: A control is some kind of sample that you use alongside your other samples or at some point in the process, again, to help you determine whether or not your process has worked correctly and whether or not you have a valid result.
MR. CLARKE: All right. We'll return to the nature of the controls that you utilized in the laboratory a little bit later. But do those controls provide you with an opportunity to determine whether or not foreign DNA; that is, DNA that's not part of the sample, is being injected into the process?
DR. COTTON: They help to answer that question, yes.
MR. CLARKE: All right. And has that gone on since DNA, that is PCR type DNA testing has gone on in your laboratory?
DR. COTTON: Yes.
MR. CLARKE: With regard to these potential influences like coughing, sneezing and touching, do you have an opinion about your ability to detect them as far as if they have any impact on your typing of evidence samples?
DR. COTTON: Yes.
MR. CLARKE: What's that opinion?
DR. COTTON: With regard to handling the samples from the point of the extraction forward, the controls will allow you to determine whether anything that you're doing has had an impact on that sample. Obviously we can't make any determination regarding what's occurred to the sample before it comes in our laboratory because then the sample is as it is. We don't have any experience in our laboratory of picking up in a sample control the types of the analysts who have handled that sample.
MR. CLARKE: So it's been your experience in your laboratory that these considerations, these things that can happen simply don't happen in your laboratory?
DR. COTTON: It's been our experience that we are not detecting them happening in our laboratory. As far as we can tell, they are not impacting on the analysis from the point that we get the sample.
MR. CLARKE: All right. Your Honor, I was going to shift gears again.
THE COURT: All right. Ladies and gentlemen, we are going to take our recess for the morning. Please remember all of my admonitions to you; please don't discuss the case amongst yourselves, don't form any opinions about the case, don't conduct any deliberations until the matter has been submitted to you, do not allow anybody to communicate with you with regard to the case. And we'll stand in recess until 1:00 o'clock. All right. I would like counsel here promptly at 1:00 o'clock. All right. And, Dr. Cotton, you may step down.
(At 12:03 P.M., the noon recess was taken until 1:00 P.M. of the same day.)
LOS ANGELES, CALIFORNIA; TUESDAY, MAY 9, 1995 1:01 P.M.
Department no. 103 Hon. Lance A. Ito, Judge
APPEARANCES: (Appearances as heretofore noted.)
(Janet M. Moxham, CSR no. 4855, official reporter.)
(Christine M. Olson, CSR no. 2378, official reporter.)
(The following proceedings were held in open Court, out of the presence of the jury:)
THE COURT: Back on the record in the Simpson matter. All parties are agai