Okay. That was something I wanted to do myself. That's how you got that. All right. Mr. Sims, would you resume the witness stand, please.
Gary Sims, the witness on the stand at the time of the evening adjournment, resumed the stand and testified further as follows:
Mr. Sims, you're reminded, sir, you are still under oath. And, Mr. Scheck, you may continue with your cross-examination.
Thank you, your Honor. Good morning, ladies and gentlemen of the jury.
THE JURY: Good morning.
CROSS-EXAMINATION (RESUMED) BY MR. SCHECK
Your Honor, I would like to start by marking a chart that I think has a label over the top "Defense hypothetical" as Defendant's next in order, and I would like--
Now, Mr. Sims, you recall on Thursday afternoon, we reviewed--based on a hypothetical that I gave you concerning an assumption of random distribution of biological material over the swatches, you made a series of estimations or approximations of the amount of human DNA in various items of evidence. Do you recall that?
Yes. And I recall too the assumption as to how much of the total swatch I was getting was part of this calculation.
There was some--we made some assumptions about amount--numbers of swatches and weights of those swatches that were not in your possession, but were in the possession of Cellmark.
All right. But based on those figures, you made these estimations, correct, as reflected in Defendant's--
Well, these--these numbers do look similar to what I said, although I don't recall the specific--
Right. Well, you recall that we--I think on Friday, I handed you a copy of this chart, and at that time, you checked it against your numbers?
Okay. And just to review then, that in terms of on the left-hand column, that reflects nanograms of human DNA?
Now, on 117, it's important to note that I did not run a specific human test on that, that my quantitation was only based on the yield gel on 117.
But in terms of your yield gel, your yield gel showed little bacterial DNA, it looked to you human?
Okay. Now, just so we're clear on this, 47, 48, 49, 50 and 52 are the items that were recovered on June 13th from the Bundy walkway?
And now, in this FBI report about environmental effects of DNA, do you recall that they reached a conclusion with respect to exposure to sunlight, eventually causes degradation of DNA and stains to the point that no typing results can be obtained?
Which--now, is that--which particular FBI study is that? Is that in the Journal of Forensic Sciences or--
Yes. I'm referring now to--I don't know if it was ever given an item number in evidence, but call your attention to page 1646.
And does that refresh your recollection as to the conclusion they reached with respect to the exposure to sunlight, what that can do in terms of degradation?
And I think you previously testified on direct examination that exposure to soil and dirt can lead to bacterial degradation of DNA in a bloodstain.
And you recall the--there was a cut-out of about three-quarters of an inch to a half-inch high in the ankle of one of those socks?
And as you indicated before, there was even some what appeared to be reddish staining or blood that was still in the--still on the sock in the area where the cut-out had been made?
And when you received the sock from the Los Angeles Police Department, you found swatches inside a tube that had been cut by Greg Matheson?
Three of the four. And on just three of those swatches, when you did a slot blot analysis, you came up with 1,350 nanograms of human DNA?
But there was no evidence in your yield gel analysis of bacterial degradation in that sock?
And so if one were to--so that's just three of the four stains where you got that 1,350 nanogram estimate from the yield gel?
Now, if we were to plot what 1,350 nanograms looked like in terms of this chart, you would have, wouldn't you agree, one of these red bars that would go like right through the top of the screen?
KEY QUOTEAnd it would be fair to say that the amount of DNA in that cut-out section of the sock was a comparatively concentrated sample I think were your words last week?
Okay. Now, you did not receive the socks for testing at your laboratory until September 26th--
And--and so on September 21st, 1994, you had no DNA results consistent with the DNA typings of Nicole Brown Simpson from that sock?
So to the best of your knowledge, there would be absolutely no factual basis for anyone saying on September 21st, 1994 that DNA tests had been performed on the socks and results had been obtained?
To your knowledge, has anyone in your laboratory, including yourself, ever communicated DNA test results to members of the press prior to communicating them to the Prosecution or the Court?
And obviously, as far as you know, no one from your laboratory, including yourself, ever said on September 21st before you--
All right. I think we're finished with that chart. Just a few real quick questions on precautions against contamination in the laboratory. Could you tell the jury what a laminar flow hood is?
Yes. A laminar flow hood is one that is designed such that when you're working inside of it, nothing gets into it and nothing gets out of it because it basically creates a curtain of air that is like a barrier to keep things from either getting in or getting out of that hood.
Yes. It's sort of a circular flow process so that--it's sort of hard to explain. I'll try to do this. But you--I think if you all know what a hood is, you're inside--it's an enclosed area inside like a little case that you're working in, and the air flow is such that it is sucked down to form this curtain and then it goes back through the back, then it goes through a filter system and it comes back down around. So you've always got this barrier of air that keeps things from getting in and getting out. And when I say things, I'm talking about dust and aerosols and that sort of thing.
And you literally would stick your hand through these--there's like holes that you stick your hand in?
Well, it's an opening. It actually is an opening. So you are putting your hands through that opening.
And the hood that you use, is the air flow such that you suck air from inside the laboratory into the hood and then out?
And a fume hood is a hood where you suck air from inside of the laboratory into the thing and then out?
Yes. And that's used when we're doing, for example, the phenol chloroform extractions because you don't want to breathe this phenol. It's not a good--or chloroform for that matter. Those are chemicals you don't want to breathe, and so you work in a fume hood to remove those fumes away from yourself.
And a laminar flow hood is the one that's designed--specifically designed to prevent aerosols and particulants from inside the laboratory from getting inside that hood?
Thank you. Now, we had a discussion about PCR carry-over contamination on I think it was Friday morning.
And just to be clear about it, I was asking you about the visibility of those fragments. Do you recall that?
All right. And just so that we're very clear, they're in a liquid; is that correct?
Well--yes, they would be in a liquid. And so the only thing you could see would be if you got a droplet or something like that on a glove, you could see them as part of that drop, but you don't really see them, the particles. They're too small.
And the smallest amount of that could contain thousands of amplicons as they're called?
Now, we talked a little bit about checks--methods that one would pursue in trying to determine whether you had contamination in your laboratory. Do you recall that?
Now, if you had in your laboratory contamination such that you could see on your DQ-Alpha strips--and we'll review those strips in a minute, but they have all these dots on them, right?
And if you saw that some of the dots were lighting up with pretty significant intensity that you knew shouldn't be lighting up in your quality assurance standards or quality control standards or your positive controls, that would be a strong indication that there was contamination in your laboratory?
If--if there were no other reason for that. For example, I've seen reference blood samples where somebody's been transfused, which creates a mixture situation. That's--that would be one example. Also, as I pointed out earlier, sometimes with this DQ-Alpha system, you will see some very weak dots because of what's called cross-hybridization phenomenon. So those things, you have to always take into account. But there are certain things you look for. For example, in your extraction reagent blank, your negative controls, if you see any dots in those, then that would signal that you have some form of contamination. That's--that's the best thing to look at.
Before we go into some of those things you mentioned, I'm just asking you about a pretty simple situation where you see on the negative control, the positive control and your quality control samples dots of not faint, but reasonably strong intensity or lighting up in a series of cases.
All right. And that would be a--certainly an indication that there may well be contamination in your laboratory?
And let us further assume--now, would one procedure one would follow to try to get to the source of that contamination, to look at the lots from which the reagents or chemicals came from?
A lot is--excuse me. The way we set up our laboratory is, we work with these lots of these kits that are provided by a commercial provider. And so we divide each shipment of those kits into a lot, and the lot--each kit includes reagents such as the--the--with the cocktail. I guess Dr. Cotton has talked about this, so I won't go into it in detail. But they have the various reagents that are used as part of this kit. We also have lot numbers for the reagents that are used to extract DNA in our laboratory. So that would be a lot of reagents that we would check out also.
Uh-huh. And let us assume in this hypothetical I gave you about searching for the source of contamination that one develops a hypothesis that maybe the source of contamination are those kits, the lots from those kits. Are you with me?
All right. And you go back to the manufacturer and you determine that there are no reports of any contamination being discovered in those kits.
Okay. In other words, the other users around the company are saying, "We didn't see that in that lot number"?
Yes. And there's a person named Dr. Rebecca Reynolds or Rebecca Reynolds? I don't know if she's a doctor.
Dr. Rebecca Reynolds. And she would be actually the person you would call to check out whether or not a lot was contaminated from Roche or Perkin-Elmer?
She's--she's one of the people that you might talk to, yes. There are other people there too that we would go through.
And if in this situation you learned from Rebecca Reynolds or some other person that there was nothing wrong with these lots--
All right. In terms of your usage, if you determined in a search for contamination from Roche that there was nothing wrong with the kits or lots, would that then lead you to search further for the source of contamination?
Roche, R-O-C-H-E, and Perkin-Elmer--now, this may be hard for me--P-E-R-K-I-N dash E-L-M-E-R.
Did you see Dr. Cotton's testimony with respect to the different kinds of proficiency testing?
I think I do remember a chart about blind. I think it was one that Mr. Neufeld prepared.
Okay. Just for benefit--I think this is Mr. Neufeld's writing, and it would be 1153. Okay. Can you see that in the back? I guess not. Let me just take a second. I'll move this over here.
Right. And that's actually not going to be visible to them as I see it. If I do that, is that--and can you--
Now--this even has Mr. Neufeld's bad spelling as I recall it. Now, would you agree that in terms of the generic types of proficiency tests, that one type is what's known as an open test?
Yes. That's--that's my general understanding and I think in the Twgdam guidelines, that's what's mentioned as open versus blind.
All right. And then there are external tests where the samples are provided to the laboratory by individuals who are independent of the laboratory and don't necessarily know the strengths and weaknesses of the lab?
And then there are internal tests which are provided by the laboratory to test itself?
And then of course--so there would be open externals, open internals, then blind externals and blind internals?
Now, with respect to the proficiency tests--withdrawn. Would you agree that as much as possible, one would want proficiency tests to duplicate or replicate casework, to be like casework?
And that in terms of all those kinds of tests, the form of testing that would be most like casework would be an external blind test?
Well, I suppose if one makes a distinction between whether or not one knows one is being tested--is that--is that--
And would you agree that proficiency tests provides one way to measure the error rate of the DNA laboratory?
And would you agree that in clinical work, DNA laboratories will often find out they made errors when doctors notify them that an incorrect diagnosis was made--
Well, you indicated on direct examination that you had some familiarity with the use of DNA typing processes and clinical medicine?
Well, in a general way, wouldn't you agree that a DNA typing laboratory that is doing work for doctors in clinical medicine can find out that they made an error in their DNA typing results if the doctor calls them and says, "Your predicted result did not match what we found when we actually did some further tests on the patient?"
Well, would you agree that in forensic work, it's harder to determine if a laboratory made an error in casework than in clinical medicine?
Well, in--based on your general knowledge of clinical medicine, would you agree--and DNA typing in clinical medicine, would you agree that in forensic work, it's harder to determine whether a laboratory made an error than it is in clinical medicine?
Would you agree that in a proficiency test, even if you don't get a wrong answer, that the test can reveal weaknesses and discrepancies in a laboratory's work that are important to note because they could lead to errors in other situations?
I--I think I'd need a little more like an example of where you're going with that. I'm not sure I understand the question otherwise.
If you take a proficiency test and there are some discrepancies in your typing results, let's say some evidence of contaminants or irregularities on a dot blot for DQ-Alpha, for example, but they don't prevent you on that particular test from getting a wrong answer. Are you with me?
It's still important to note what those discrepancies or irregularities are because on another test with another set of samples, those could lead to errors?
And that's one of the things that proficiency tests can help a laboratory identify?
Now, the only proficiency tests that have been conducted in your laboratory from external sources are open proficiency tests?
And you're familiar with the recommendation--the section of the national academy of sciences report that talks about laboratory error rate?
And is that a section that you would rely upon on forming your opinions concerning laboratory error rates in external blind proficiency testing?
Well, the problem that I have with regards to the NRC is, they're not clear on what a blind test is in their own definitions.
Well, have you ever looked at the glossary of terms at page 171 of the NRC report?
It's overruled. He can direct his attention to something and attempt to lay a foundation here.
Now, you just said that one of the problems you thought you had with the NRC report is the way they define the different kinds of proficiency testing?
Would you agree that in the glossary of terms, that the NRC defines the different kinds of--
Would you rely upon the definition in the glossary session at page 171 of the NRC report in terms of its definition of proficiency testing?
Sustained. The question is not appropriately phrased, counsel. It's not prospective. It's "Have you."
All right. Have you relied on the section in the glossary, definition section of the glossary for forming your opinions about what the NRC means with respect to proficiency tests and how they're defined?
In forming your opinions with respect to proficiency testing and DNA testing, would you rely upon the glossary section definition of the NRC report--
--in forming your opinions? Looking at the glossary section, does that refresh your recollection as to how the NRC defines proficiency tests?
Have you relied. Have you relied on the definition section of the NRC report with respect to proficiency testing?
Have I relied on the NRC to tell me what those definitions are? Is that the question?
You have your own definition. All right. But you gave us testimony a second ago about what you thought the NRC meant, how it defined proficiency testing.
All right. In deciding what the NRC meant about different kinds of proficiency testing, had you previously relied on the definition section in the glossary?
Not in the definition section, but there's other places in this writing where it's very confusing to me.
Okay. Now, getting to the section of the report that deals with laboratory error rates.
All right. The section of the report dealing with laboratory error rates starting on page 88 to page 89, do you rely upon the national academy of sciences report with respect to laboratory error rates how laboratory error rates should be measured? Do you rely upon that in forming your opinions concerning error rates and DNA typing?
On their--I think I need more definition from you on that. I mean, are they saying that you should take a look at proficiency rates or proficiency error rates? I would agree with that.
All right. Do you rely upon that section which states that error rates ought to be determined through external blind proficiency testing?
That's an inappropriate way to phrase that question, counsel. No. Have a seat, Mr. Harmon.
I was asking Mr. Harmon to have a seat. But--but, counsel, we're not getting anywhere with this. Why don't you just ask him about the advantages, disadvantages about the different types of proficiency testing and let's move on.
Has to rely upon it in forming his opinions, counsel. You don't have the foundation.
Would you--all right. Let me just look--just call your attention--you're saying some parts of what they discuss about laboratory error rates you would rely upon?
No. No. Unfortunately, I can't ask you that question. I have to ask you the question, have you relied upon those sections of the NRC report dealing with how to measure laboratory error rate in forming your opinions?
Okay. Thank you for the no. Now, in terms of--you took a few proficiency tests, external proficiency tests that were provided to you by the College of American Pathology and the Collaborative Testing Service?
Actually, the collaborative testing service is correct. The other ones that we did were through the United Kingdom branch of Cellmark.
Okay. Now, in either the--what is the--there's an acronym for the--the IQAS is the Cellmark acronym?
I don't use it, but I think there is--International Quality Assurance Scheme or something like that.
Now, in these tests, did you receive degraded samples, samples that were substantially degraded as specimens to analyze?
All right. But it is substantially degraded specimens that we're dealing with certainly with respect to the Bundy blood drops in this case?
Well, I don't think no. 52 was substantially degraded. I think some of the other Bundy drops I would agree with that. 47, 48, 49 and 50 I think would be correct, but 52 I don't think was substantially degraded.
Well, again, I--I don't think I can answer that because all I did was a slot blot on it. But I know that Dr. Cotton was able to get an RFLP result out of it. So that tells me it's not substantially degraded.
Well, the RFLP result--withdrawn. If an RFLP--an RFLP result can be obtained on as little as 25 to 30 nanograms of human DNA?
And ordinarily, a blood drop, a drop of blood would contain how many nanograms of human DNA?
What would be your expect--expectation--withdrawn. You--in August of this year, you performed an initial inspection of these swatches?
And after looking at the yield gels, but before doing the slot blots, you offered some testimony with respect to your expectations as to how much DNA you would find in the Bundy blood drops?
I don't--I don't recall it being an expectation. I think at that point, we had discussed potentially how much we had found. This is back in August, right?
And based on a yield gel, for example, for items, you were getting readings of as high as 150 nanograms of DNA, of high molecular weight DNA based on the yield gel?
And when you subsequently did the slot blot to find out how much human DNA was in the sample, you found out that it was substantially less than 150 nanograms?
And what that did is that when you did that slot blot, you realized that there was a lot more bacterial degradation in these Bundy blood drops that even you had initially anticipated when looking at the--at these swatches and doing your yield gels in August?
Now, getting back to the question about proficiency testing, I take it you are agreeing that the proficiency tests that you received from collaborative testing service and IQAS did not involve substantially degraded samples?
The California Association of Crime Labs proficiency tests, however, you know those did involve substantially degraded samples?
Do you know if the CACLD proficiency tests involved substantially degraded samples?
And in fact, when they--in preparation of the samples for the CACLD proficiency tests, some of those samples were deliberately subjected to severe environmental conditions in order to degrade them?
But the approach of CTS and IQAS in the proficiency tests that you take is not to intentionally degrade the samples?
And wouldn't you agree that in casework, laboratories such as yours are routinely encountering degraded samples in terms of performing your DNA analysis?
All right. In your lab work, do you not encounter on a routine basis in your cases substantially degraded specimens for purposes of performing DNA analysis?
And wouldn't you agree that it would be--withdrawn. And wouldn't you agree that well-designed proficiency tests that are intended to duplicate what you actually get in casework ought to involve degraded samples?
Would you agree--I under--Mr. Sims, I understand that you can only subscribe to those proficiency testing services which are available. Fair enough?
All right. And these questions are really directed at the kinds of tests that are available for you to take.
But in terms of the tests that are available for you to take--withdrawn. In terms of designing a proficiency test that would replicate, duplicate what your lab actually encounters in casework, wouldn't you agree it would be a good idea to have specimens that are degraded?
Well, I think it's a somewhat complex issue because on the one hand, when we're doing RFLP proficiencies, it only works with samples that are not substantially degraded. So if we're testing people for their RFLP ability, then it doesn't make sense to me to do work with degraded samples because you won't get an RFLP if it's substantially degraded. On the other hand, I--I see no problem with looking at degraded samples if you are going to look for PCR type results. And this whole--this whole issue of designing proficiency tests that fairly tests all the laboratories is something that, you know, is being worked out. I mean, there are--there are some questions there about what different types of samples one may want to look at so that everybody is fairly tested. That's an issue.
In any of the open proficiency tests that you have done, were there mixtures of blood on a bloodstain where one source contributed a considerably smaller amount than the other?
All right. Were there mixtures in any of these open proficiency tests that you took of bloodstains where the contribution of one--you found out later the contribution of one of the contributors was much greater than the contribution of a second or third contributor?
All right. Have there been significant differences in the contributions that you were able to detect?
I recall in the laboratory, that there was one that was submitted where they tried to catch the lab as to whether or not they could detect two stains that were mixed like that. I think it was one of the CTS ones.
I--I think that was the scenario. That was not done by me, but somebody else in our laboratory had one where I think that was the issue, that whether or not they could detect this mixing.
I think it was two bloods. I'd have to check because, again, that was not my personal test. But I think we had something like that come through the laboratory.
I don't know the numbers off hand. I would have to go back to the lab and look into that.
Now--but you personally, for example, have taken no tests involving the mixtures of blood where one source contributes a much greater amount than another?
And have you ever taken a proficiency test where you were trying to detect genotypes in a mixed bloodstain where there was more than two contributors, where there was three or four contributors?
But in this case, you've been asked to analyze bloodstains that at least the Prosecution is claiming has as many as three sources?
And you have never taken a proficiency test, even an open proficiency test that involved such a situation?
Now, wouldn't you agree that in terms of DNA typing, that--particularly PCR base typing, that mixtures present special problems?
Well, there's two things. You have to be able to detect the mixture and then you have to be able to interpret the mixture.
Now, I notice on direct examination that you never used any of these dot blot strips to explain how you got your results. Am I correct on that?
Right. But that's how you got all these DQ-Alpha results, is using this blot dot strip?
Now, what I'm going to put up on the elmo here is--to start with is just a dot blot strip. And what I would like you to do, Mr. Sims, is explain to the jury, if you go through it step by step, how one reads one of these strips.
Okay. Why don't we just use for a second the one at the top that is labeled DNA 17C. Okay?
And starting from the left to the right, could you please tell the jury--there are a series of numbers across this strip, correct?
All right. And could you tell the jury what each of these numbers represents and how one gets a reading off one of these strips?
And if--maybe we should even use--do we have one of those telestrator things? Maybe--we're trying to simulate a direct examination, Mr. Sims. Maybe you could come down and stand next to me or stand over here. And you know how to use this point maker now?
Sure better than I. I'm sorry. There you go. Okay. Starting with the one that says DNA 17, could you tell us what--starting on the left, what the 1 represents?
Okay. The 1 is for the overall type 1 probe. In other words, we'll talk later about the subtypes of the 1. But the first thing is that that's an overall 1 probe that's--now, keep in mind the probe in this case is already on the strip. That's what the manufacturer does. They provide you with a strip that has the probe already on it. You'll recall we talked about RFLP. We put the DNA onto the strip and then we hit it with the probe. Well, here, we put the probe already on the strip--the probe is already on the strip and now we hit it with the DNA. This is why it's called a reverse dot blot.
And wouldn't it be fair to say that--that the way this PCR base method works is, is that you take the--you extract the swatches, right?
And so what you're really doing is, you're pouring that so-called amplified product over the strip?
And then when you pour the amplified product over the strip, you see which of these blue dots light up and which don't?
Okay. So what I take it you're saying is that starting on the far left-hand side of 17, the blank one, that there's a dot there that we can't see lit up, correct?
So point--that's where you have the pointer right now. Now, underneath--right next to that 1, there's a little--there's a little piece of probe, right?
A dot of probe. When you pour the amplified product up, if there's any genotype that is part of the 1 system here, okay, that dot should light up?
And there are subtypes that we'll discuss as we go across this strip of the 1. There's a 1.1, a 1.2 and a 1.3?
So if there was anybody that had a genotype for the 2 and you poured the amplified product on the strip, the blue dot should light up?
So if we pour amplified product on the strip and there's anybody that has a 3 allele, right, that should light up?
So if we pour amplified product on the strip and somebody has a 4 allele, that blue dot should light up?
Okay. This is an important dot right here. This is called the c or control dot. And the point for the control dot is, that tells you first of all that you had enough DNA on the sample to see both of the alleles in a sample. In other words, there's enough DNA to get a result, a typing result. It also is useful in that it can be used to gauge the relative contributions of samples when you start to look at a mixture situation. And we'll talk about that I think later on if I'm guessing where you're going with this.
Well, let's talk about that just for one second, see if we understand this. So this c dot, they call that the "All control," right?
So the theory is, is that when you pour amplified product over this strip, that if this c dot lights up, right--
--then that means you're not missing any potential alleles because if this dot lights up, then you should be detecting all the other potential alleles in the mixture?
Now, of course, as we're going to get to in a second, when you have a mixture, that c dot has less utility as a control, doesn't it?
No. I think, for example, in Dr. Blake's article, he talks about using that as a convention and looking at the intensity of the dots relative to the C. So we--we--I wouldn't say it's--
Excuse me. Counsel, you need to not interrupt his answer. You need not to talk at the same time.
Let me put it--let me formulate the question for you this way. When you have a mixture and you pour the amplified product over the c dot, this c dot can be lit up by the primary contributor of the mixture, correct?
And so if there is a secondary or a second contributor to the mixture or a third contributor to the mixture or even a fourth contributor to the mixture that have less DNA from those sources--are you with me?
The c dot won't tell you about whether you're missing any alleles from the second and third and fourth contributor because the c dot is being lit up by the primary contributor?
And in that situation, where you have such a mixture, the utility of the c dot control in terms of telling you whether you're seeing all the alleles is not as good as it would be were it just one person?
Well, again, I mean, you can only talk about what you can see there. But your point is well taken, but you can't say much more about those very weak allele dots.
Okay. And of course, what we're dealing with in this case, as we'll discuss in a minute, are mixtures which involve at least three contributors according to the analysis the Prosecution has put up here?
That's the 1.1 dot. See, now we're getting into the subtyping of the 1 alleles because the 1 allele can be broken down into the 1.1, the 1.2 and the 1.3.
And when you're seeing a 1.1, you should also see that 1 over at the left hand, left-hand side, right?
All right. And when you--when you make that caveat, if it's a real 1.1, sometimes in this system, there are limitations to this system?
And one of the problems that an analyst has with this system is, sometimes these dots light up faintly and it is difficult to tell whether the dot represents a real allele in the mixture or it is what is I guess in your business called an artifact?
An artifact would be, for example, if you are seeing some signal at one of these dots that's very weak, but it's not really part of the actual type.
So would it be a fair way to distinguish it is that sometimes you see a dot light up and you know it's real in the sense that it actually represents the DNA from the original source?
Really are seeing the type? And then sometimes these dots can light up and it's not real, it's an artifact?
Now let's move over to the next dot. Now this gets a little complicated, doesn't it?
Yes. This is--this is where the system gets complicated. And the basic limitation is is that there is not a unique probe for this 1.2 allele. So we don't have a single dot that says this is what you see, light up if the 1.2 is there. So what you have to do is, you have to do a little bit of logic here and you have to do a little bit of logic to decide whether or not the 1.2 is there against the contribution here from the 1.3 or the contribution from the 4. And it's hard to do it without showing you an example. But I think you'll recall seeing a lot of my results where I said possible 1.2, possible 1.2. That's because you can't always say that the 1.2 is present. For example, if the 4 allele is definitely present, you may have trouble saying could there be a 1.2 there also. And that's why you saw a lot of those results in parenthesis and that's one of the limitations of the system, and I have to make the assumption that that result--that dot could be there, that type could be there. I just can't detect it in a mix.
But let's--let me try to break it down as simple as we can for reading this particular dot. What that dot represents is that, if that dot lights up, you could either have the 1.2 allele?
Or combinations. But one way you can double-check is, if that dot lights up and the 4 dot lights up, you know that there's a 4?
And if this particular dot lights up and the 1.3 right to the directly to the right of it lights up, you know you have a 1.3?
And then sometimes you might be lucky enough by process of elimination to determine if you have a 1.2?
Okay. Moving over to the right--and this is a dot of some significance to your laboratory I take it. That is the 1.3 dot?
Yes. If the 1.3 is there, you should definitely see that dot light up. Sometimes this is the one that is the most useful indicator of this cross-hybe phenomenon that I talked about because it's very, very close in its DNA sequence to some of the other alleles. And so you're--if you see any of this weakness in the background, that could be an artifact, and that's what you really key on when you look at these types of strips.
So in other words--you anticipate I'm going to ask you some questions about interpreting this 1.3 dot, don't you?
And your laboratory does have some problems with this 1.3 dot lighting up persistently in lots of tests, and it's hard--it's been hard for you to determine why that's happening?
All right. Let's--let's move on from the 1.3 dot. What's the one to the right of it?
That's called the all but 1.3. And that's used to distinguish if you have a situation where you're trying to distinguish the 1.3, 1.3 homozygote. That's what that dot is for. It's again part of the logic.
Right. Now, remember we had--we discussed--when we were discussing PCR carry-over contamination--
All right. And we were discussing the number of--those billions of fragments that we called amplicons?
And if you recall, we used an example where the starting material contained DNA that was 1.3, 1.3?
All right. Now, let's--starting back to that pyramid where you have a sample that has 1.3, 1.3 in it, okay?
Yes. If they all--now, there--you have to give me the exact conditions. They're all getting in there?
I'm talking about a situation where you have billions of fragments that were just 1.3, 1.3.
Your Honor, objection. Could we keep the comments down? Could you instruct Mr. Scheck--
And on 1133, our hypothetical was, we were starting with biological material that contained, for this DQ-Alpha system, 1.3, 1.3.
And we discussed how on just one PCR run, you--in one of those little tubes, you would create 4 billion 290 million fragments of 1.3, 1.3; is that correct?
But again, I should point out that we're not talking about in any case, we're starting with just one fragment, right. You're saying theoretically you end up with billions of copies.
Now, if we had the scenario we were talking about the other day, samples of 1.3, 1.3, how would it look on that chart? The 1 would light up in the far left-hand column, right?
Now, in terms of PCR carry-over contamination, if there were a problem of PCR carry-over contamination at a laboratory, such that through repetitive typing, there was some 1.3 amplicons in the laboratory--are you with me?
--that could account, in terms of typing, for the 1.3 lighting up persistently in various strips, even if faintly?
Well, again, that's why you run all those control strips. Because those are all negative, that tells you that you're not seeing this consistent problem.
Okay. Now--okay. Thank you very much for this. And maybe you could return to the stand, and we'll move a little further here.
Now, we were talking about mixtures and how to interpret them. Do you recall that?
Now, there are different kinds of mixtures that DNA laboratories encounter in their casework?
And the one that has been done--withdrawn. A very typical kind of case for a DNA laboratory involves a sexual assault case?
And a mixture in a sexual assault case, if let's say there is one perpetrator and one victim, ordinarily involves DNA from the sperm of the perpetrator?
Yes. Those are the--in this case, you'd be talking about the cells that line the vagina.
Right. So ordinarily happens in a sexual assault case is that a swabbing is taken from the victim of the rape, and on the swab, there is evidence of sperm and also cells, epithelial cells from the vaginal wall of the victim?
And that's the typical kind of mixture that forensic DNA laboratories will encounter in such sexual assault cases?
And when you're dealing with that kind of a mixture, you can do something that's known as a differential extraction, correct?
And that's--I mean literally, what you can do is, you can take the mixture and you can look at it under a microscope?
And then what you do in the differential extraction is, you literally take some kind of a detergent and you pour it over the sample, correct?
All right. But literally what that means is, you first put in a detergent that is not as strong as a second detergent that you're going to put in, correct?
Well, it's--it's a little more involved than that. It--what it really comes down to is--
In a differential extraction in a sexual assault case, what you can do is first extract the DNA from the epithelial cells, correct?
And you do that by literally pouring in this chemical, and that will burst open the cells from--the epithelial cells and you can drain out the DNA from the victim?
Well, yes. Basically what you're doing is, in this differential extraction process is, you're first getting out the DNA from the female contribution from her cells while the sperm heads--until you add another reagent, the sperm heads, because their DNA is packaged differently, they are resistant to that differ--that first Lysis that you mentioned. So they stay, the DNA stays with the sperm.
So then you can pour in a stronger chemical and you do a Lysis or you burst open the sperm cells, correct?
And so in that fashion, you can with some assurance--doesn't always work perfectly--but with some assurance, you can separate the sperm DNA from the epithelial cell DNA from the victim?
Yes. Again, it doesn't always work perfectly, but you can get an idea of what the mix is that way.
And in that kind of a mixture situation, you--you can then sort of have a backup because if you take a blood sample from the victim and you compare it to the reading you get from the epithelial cells, you have sort of a back-up check to know that your process is working correctly?
And that is of considerable assistance in interpreting a mixture in a sexual assault case?
And it's in some ways analogous to doing DNA testing in a paternity case where you have back-up systems where you know what the genetic--the genotypes of the father is and you know--or the punitive fathers and you know what the genotype of the mother is?
Let me withdraw that question. Let's just get to the bottom line here. Would you agree that mixtures involving bloodstains from two or three or four contributors, you can not perform a differential extraction like you can in a sexual assault case?
You can not put that bloodstain under a microscope the way you can in a sexual assault case and literally see the different kinds of cells that are contributing to that mixture?
If you have a mixture of a bloodstain and saliva together, you can not look under a microscope to look at that bloodstain and see what cells come from saliva and what cells come from blood?
Well, now that's incorrect, because when you're talking about blood against blood, that's true. But saliva, as you mentioned earlier when we were talking about sneezing, has these epithelial cells, and one could look under the microscope and make an extract of a bloodstain just like one would make an extract of a semen stain and look at the microscopic charac--you know, the features that are there, and you might see that there are epithelial cells that could be contributed to saliva for example.
I think I did that in one case. I don't recall doing that in my DNA work, but I can recall doing some kind of micro exam on--for example, we--it's not unusual to look at a bloodstain where there may be a blood and semen mix. That's not an unusual--
That would not be an unusual occurrence, to have a blood semen mixture, and so one would do a microscopic exam for that purpose.
Well, depending on whether or not the person has sperm. I mean, it may be a vasectomized individual for example.
Counsel, it's really--let's just go back to the blood mixtures, please. We're not dealing with any other mixture here.
Did you examine under a microscope the bloodstain mixture to determine whether there was--you could see anything that you would attribute to the epithelial cells of saliva versus cells from bloodstains?
All right. And you're actually saying that's something that you think could be done, but wasn't done?
Now, bottom line, would you agree that as opposed to a sexual assault case where there's a mixture of sperm from one contributor, non-vasectomized individual, and a vaginal swab from one victim, all right, as opposed to that situation, interpreting DNA results from bloodstain mixtures where there are more than two contributors, all right, that that second situation is a much more challenging application of this technology?
Well, it's more challenging in terms of saying what could go with whom for example. That's true, although sometimes even with those types of mixtures on RFLP, you may be able to sort something like that out.
But bottom line, the two or more contributor bloodstain mixture, to use simple terms, is harder in terms of trying to figure out who are the contributors?
Now, you received swatches from the Bronco numbered 23, 24, 25, 29, 30, 31 and 34, correct?
I believe those numbers are all correct. Some of those--now, 23, I don't think we analyzed for example.
Do you know if all those samples, based on the writings that you received, were collected on June 14th?
All right. I'm going to ask you to assume that all those samples were collected on June 14.
And you received another set of samples, 303, 304, 305, which were swatches from the console, correct?
And those I'd like you to assume--well, do you have any notations about when those were collected?
It was my understanding that they were collected later. I don't know the exact date.
About two and a half months after the first set of samples that we discussed were collected.
Well, let me--maybe my month estimate is off. I would ask you to assume that the first set of samples that we discussed up to 34 were collected on June 14th, 1994, and then the second set of samples, 303, 304, 305 from the center of the console were collected on September 1st, 1994.
Well, I think that August 26th, they were first examined. September 21st--September 1st, they were actually swatched by Mr. Matheson.
Now, looking at these samples, I'd like you--do you know--I'd like you to assume that no. 30 that's labeled here "Center console" was collected on June 14th and no. 303 was collected at a later date from the same area as 30.
All right. Let's take our break now, let you look at the photographs. All right. Ladies and gentlemen, please remember all of my admonitions to you; 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. We'll stand in recess for 15 minutes. Mr. Sims, you may step down. Mr. Scheck, why don't you point out that board. All right.
if we were to plot what 1,350 nanograms looked like in terms of this chart, you would have, wouldn't you agree, one of these red bars that would go like right through the top of the screen?
That's correct. [confirming no DNA results from the sock existed on September 21, 1994]
Yes. That would tell you that you may have a contamination problem.
That's true. [confirming the c-dot cannot verify allele completeness for secondary/tertiary contributors in a mixture]
The NRC report is not coming in through this witness.