Thank you, ladies and gentlemen. Please be seated. The record should reflect that we have been rejoined by all the members of our jury panel. Dr. Cotton, would you resume the witness stand. And, Mr. Clarke, you may redirect.
Thank you, your Honor. Good afternoon again, ladies and gentlemen.
THE JURY: Good afternoon.
REDIRECT EXAMINATION BY MR. CLARKE
Dr. Cotton, with regard to these proficiency tests that you were asked questions about earlier today, can you estimate for us or otherwise tell us the number of proficiency tests that your laboratory has taken since 1989?
I made a count, assuming I counted correctly, since the beginning of 1990 till the end of 1993, comes to about 104, and there have been ongoing tests in 1994 and continuing into `95, but they're not reflected in the documentation I have with me. So I didn't include those.
Now, is that just the number of different tests that the laboratory has taken, proficiency tests?
With regard to these--and I'm sorry. What was the number again since 1989 through 1993?
How many different samples--do you have a count of the total number of different samples that those 100 plus tests included?
Of those 466 samples since 1989, that is proficiency test samples that have been tested, how many errors has the laboratory made?
There are no false positives and no incorrect exclusions in the remainder of those samples since 1989.
KEY QUOTESince 1989, has your laboratory made or have they typed any false positives in any test?
Your Honor, may I just ask for clarification? Is this proficiency testing? I just--
I'm sorry. Could the witness be allowed to conclude her answer? I believe she was in mid sentence.
The only measure we have of a false positive or a false exclusion is on a proficiency test. I obviously can not tell you in a case because we--as was pointed out earlier, we don't know what the result is supposed to be. I can't tell you whether in the number of cases that we done--have done, whether there are any because although it's possible you would be able to pick it out, it's not a guarantee that you would be able to pick it out by any stretch. And, therefore, I can only tell you in reference to the proficiency tests, and I can't tell you any further than that.
Perhaps I misspoke. Actually I was addressing myself only to proficiency tests and those tests that you've taken since 1989.
There are no false--additional false positives and there are no incorrect exclusions in the proficiency tests since 1989.
Incidentally, as far as this area of proficiency testing, what role if any did your proficiency tests have to do with your accreditation by the American Society of Crime Laboratory Directors?
Like the TWGDAM guidelines, the ASCLAD lab requires that each analyst take two tests per year, and one of them must be from an approved--an ASCLAD approved proficiency test provider. And we must sign documentation agreeing with--that we will give those results back to a committee--back to ASCLAD--it's a committee within ASCLAD lab--for their review. So not only are they being reviewed by our laboratory, but they're being reviewed by ASCLAD.
Was this or did these proficiency tests play any role in your accreditation process?
We--if we had not been doing the level of proficiency testing that we have, our lab would not have been accredited.
Now, I'd like to change topics to--and do you recall a series of hypothetical questions asked you by Mr. Neufeld about various swatches taken from the Bundy crime scene?
And in particular, do you recall being asked questions about the various blood drops starting from the drop closest to the victims' bodies, no. 47, through and including the remaining drops, 48, 49, 50, and then finally 52 out in the driveway area?
Do you recall his questioning you about the possibility that each and every one of those samples was cross-contaminated by contact with swatches taken at a different scene; mainly, the Rockingham home?
If both swatches were wet and they were in immediate contact with each other presumably because they were wet, you could have some exchange of material. If they were dry, that would be harder and you might have to have sort of an excess of material on the swatch, such that some was basically sort of flaking off. But it would be harder if they were dry than if they were wet.
Now, I believe you described during your cross-examination that that type of transfer from one swatch from one location, that is seized at one location, to another location seized from another location was scientifically possible; is that right?
Would it be the case--and first of all, you have already testified about various results from the Bundy crime scene; is that right?
And you described, for instance, typing results from the shoeprint, which is item 56?
Now, your Honor, with the Court's permission, I would like to use the Bundy results board at this time. And I believe that's People's exhibit 259.
Deputy Smith, why don't you grab that other--I think we need it up just a bit. Great. Thank you.
Now, Dr. Cotton, can you see those results without--we won't be going into the individual types and their results, but can you see basically each of those item numbers beginning with 47 from where you're seated?
Let's start with item no. 47, the first drop by the victims. And what I'm going to ask you is, for the hypothetical, this hypothetical possibility of a transfer occurring from one set of swatches seized at one location to these particular set of swatches, would it be correct that these individual items, first of all, would have to be collected; in other words, collected by some evidence collector at the Bundy crime scene? Let's start with item 47.
For that hypothetical to be true about this cross-contamination, would the DNA in that particular sample, again, the first drop by the victims, no. 47, have to degrade to the point that you could detect no DNA whatsoever even by PCR?
Would that item in terms of the swatch or swatches for each individual item then have to come into contact with these swatches from a totally different scene and a different item number?
Is touching enough or does something have to physically happen from one swatch to the other swatch?
What actually has to transfer from one swatch to the next swatch for this hypothetical to actually be true?
Well, given that the swatches are bloodstains, white blood cells have to transfer--I mean, you wouldn't have just white, but you would have to have blood cells transferring off one swatch and on to the other.
What would have to be the quantity and quality of these cells that have gone from one swatch to the other swatch so that you could only detect the material that transferred?
The material on the swatch from which the contamination was coming would have to be of sufficient quantity and quality to do the testing--to appear on the final test. So given that one now had completely degraded so you couldn't test it, you would have to have enough transfer from the other swatch, enough DNA of sufficient quality to be able to now see it on the test.
And then ultimately--and you've described that final step. Ultimately, for this hypothetical to be true, you would then have to go through a typing process and only detect the types from the swatches that supposedly cross-contaminated, for instance, item no. 47?
Now, would that same occurrence for this hypothetical to be true have to have happened to item no. 48, the next Bundy walkway drop?
Now, let's talk in a little bit more detail about item no. 52. What do we know about the quantity and quality in item no. 52 in comparison to 47, 48, 49 and 50, the earlier drops on the walkway?
We know that the quality of the DNA in 52 is sufficiently good to give an RFLP banding pattern. That is, some of the DNA is good enough to do that. And it--and you can--you can see on the mini gel that it's much better than the 49 and 50 which were also run on mini gels. And then as far as 47 and 48, that--that was not good enough either. So basically 52 is in much better shape than 47, 48, 49 and 50.
Does that mean the DNA transferred by this hypothetical from another swatch at another scene to the material in item no. 52 would have to be some amount in quality of DNA in excess of the remaining drops?
Is there any way to describe that difference in how much and what the quality of the DNA would have to be?
Well, in terms of quality, it would--there is a sub--I'm--I have a very good recollection of what 49 and 50 look like for some reason. So I'll just use those as an example. The difference in the level of degradation between 49 and--49 and 50 look about the same, and they are very different from 52. In terms of quantity of DNA in those samples, I would have to go back into the case folder and look at the amounts and give you--to give you a good estimate.
Okay. In any event, it would be greater than the remaining samples, 47 through 50, that would have to be transferred in the hypothetical? I'm referring to the quality and quantity of DNA.
In terms of the quantity, are you saying is that different for 52 than the others?
In terms of what you can detect, yes. In terms of actual mass amount, it may not be any different.
The actual weight, that is of the DNA that you have, which is measured in terms of nanograms, it could be a similar amount in 49 and 50, for example. It's just that it's very degraded and the other is not.
Okay. Now I would like to turn your attention to item no. 56, the shoeprint that's also listed on this particular Bundy crime scene results board. As far as that particular item is concerned, is there any indication whatsoever of cross-contamination similar to that on 47, 48, 49, 50 and 52 in terms of DNA type?
Well, the other--47, 48, 49 and 50 are consistent in type with Mr. Simpson. 56 is consistent in type with Nicole Brown. So if all of those samples were contaminated, they couldn't have all been contaminated from the same source.
KEY QUOTEAnd in fact, at least one of them--let's take the DQ-Alpha alleles. Is it true that there is one DQ-Alpha type that's not even present in item no. 56, the shoeprint?
Now, with regard to this hypothetical--and first of all--well, let me rephrase that question. With regard to this hypothetical, do these unstained controls play any role in determining whether or not this type of transfer could have occurred?
Well, they would if they were out and about at the same time that you're postulating the other contamination occurred because they don't have any DNA on them, the ones that we tested.
Let me put it in the form of a hypothetical to you. If those unstained controls--and let's assume there are unstained controls for these various items of evidence, 47, et cetera--and that those were processed in the same manner as the bloodstains, would those unstained controls in terms of if they detected no DNA, typeable DNA, provide you any information about whether or not this hypothetical cross-contamination transfer actually occurred?
Well, part of the objection is the "et cetera." I mean, maybe he should spell out which samples he's referring to.
All right. Instead of that et cetera, 47, 48, 49, 50 and 52. Do the unstained controls provide you any further information if what I described to you is the case?
If the unstained controls were processed in the same manner at the same time as the actual samples, then you would have to postulate that the contamination only occurred on the actual samples and didn't occur on the unstained controls. So it would be a very specific contamination, not just sort of affecting everything.
And by "processed at the same time," do you mean collected, allowed to dry, repackaged, et cetera?
That's the second time I've used the word "et cetera." But through those stages that I just described including packaging?
Do these unstained controls in this case represent or are they an additional safeguard as to the accuracy of DNA results in this case?
The unstained controls tell you one thing. That is, that there was no DNA on a spot adjacent to where the stain was lifted from. I don't think they say anything beyond that.
Are these unstained controls, are they to show the presence or absence of bacteria? Is that what you use them for, for instance?
No. We don't have--I suppose you could test for the presence of bacteria on those unstained controls. We don't--
Incidentally, in your laboratory, in the controls that you tested, that included item no. 49, that is an actual unstained substrate control for one of the Bundy walk stains, no. 49?
We received a sample, was labeled item no. 49. It was sent to us with other samples that were indicated that they were unstained controls. It didn't have "C" or control written after it.
Item 7 control, item 12 control, item 49, doesn't say control after it, item 56, doesn't say control after it.
Are you aware that any other unstained controls were tested by any other laboratories in this case?
Dr. Cotton, I would like to offer you a hypothetical. That if in fact, with regard to these particular items at the crime scene, that is the Bundy crime scene--actually, let me rephrase that.
Dr. Cotton, I would like you to assume that with respect to this particular results board, the Bundy results board, that with regard to each of the items, except for purposes of this question, 84-A and 84-B, that there was an unstained control seized for each of those particular items. All right?
That the results of those unstained controls showed no detectable DNA present. All right?
Does that information assist you in reaching any opinion about whether or not the cross-contamination possibility posed by Defense counsel occurred in this case?
Now, I would like to shift your attention if I could, Dr. Cotton, to questions posed to you about the possibility of a blood tube, that is a tube containing known DNA, could have been spilled or placed or inadvertently mixed with the same swatches, that is from items 47 through 52, the Bundy walkway stains. Do you recall those questions?
For that to have occurred and for you to have obtained the types that you described, again would the DNA in these various walkway stains have to degrade so that you could detect no DNA? Actually let me rephrase that. Be able to detect no DNA types.
Would it also be correct for that hypothetical to be true that you would then obtain only the DNA types from this spilled or otherwise contaminated tube blood?
If this occurred, that is, these spills or placement from a tube, would you expect these particular swatches from 47 through 52 to have the same quantity--let me rephrase that--to have the same quality DNA?
There would be a reasonable expectation that if that occurred, they would have close to the same quality of DNA.
Well, I could think of two scenarios. One is, the blood gets on there, it dries, and once it's dried, nothing much happens to it in terms of degradation, in which case you would expect to have the same quality of DNA. The only way I can postulate that that wouldn't be the case would be, the blood gets on the swatches and it doesn't dry very rapidly, and, therefore, something that's already on the swatch then differentially degrades the DNA on one swatch as compared to another; and in that case, you wouldn't obviously expect that they would all be the same.
Did you see, in terms of these stains, the same quality of DNA, this is again the walkway stains, 47 through 52, or did you see differences in quality of DNA?
Did you detect or did you determine if the DNA quality from these swatches, 47 through 52, was the same or was it different?
You can see the differences on the mini gel in terms of how degraded the DNA is in those different samples.
Was there a difference--and let's--you know, if this would help you, let's take 47 and 48. Were there differences between those two, or if there's a better way of describing this difference, please tell us how.
If you want me to be more precise about it, you'll need to let me get out the pictures so that I can look at them.
Could you start with item 47 and tell us what would be the easiest way to make this comparison between that first walkway stain by the victims and the remainder?
Well, I'll go down item by item and sort of try to give you the level of degradation that we can see on the mini gel versus sort of like not very much, a moderate amount or a lot.
You have to keep in mind that this mini gel isn't assessing human DNA, it's assessing total DNA, and, therefore, there's--you know, I can only tell you what I can see. I can't tell you anything about whether what I'm--based on this result alone, as to what I'm seeing is human or not. Okay. Item 47--and again, I'm taking a minute because I have to translate numbers here and also count. Item 47 is very degraded. Item--item 49 and 50 are very degraded. Item 56--
Actually what I am going to ask permission to do, your Honor, is to display to the jury just briefly the photographs of each of these items and ask the witness to describe what they mean as far as this opinion.
No. Photographs of the actual test results from determining how much DNA is present.
We can if you'll give me just a second to pull out the--what I have to do is give you the originals and then pull out the sheets from my copies that will tell me what samples in what lane.
Your Honor, an additional objection based on her testimony that a lot of it isn't even human DNA--
All right. Could we, your Honor, for purposes of this utilize the originals and obtain copies and at some point substitute them? These are I believe--
All right. Dr. Cotton, you have given me two pages. Which one would show--that is, which page and which photograph would demonstrate item no. 47, the first drop?
Dr. Cotton, showing you a photograph that's now on the screen that will be People's exhibit 263, what's that a photograph of?
It's a photograph of the small mini gel that was used to look at the DNA that was extracted from the samples that were loaded on there.
If I give you the pointing arrow and give you the podium, can you describe for the jury, please, what particular lane we're looking at? And then I'll have you describe what this process actually shows.
First of all, Dr. Cotton, with regard to this photograph, what would you call this photograph? What's it of?
It's a photograph of the mini gel using the DNA samples before they were digested with the restriction enzyme.
Now, is there a way that you can show us--and let's start with--I'm sorry--item no. 47, the first walkway drop. Can you indicate where you would look for results on this photograph?
Are we on here? The top of the gel is up here (Indicating) And you see--see--the best place you can--see right here, that little inden--that's an indentation where the sample is loaded and so is this and so is this. And you can't see them quite as well over here, but they go all across the top. So the person who did the work recorded what sample she loaded in this lane and what sample she loaded in this one and this one and so on. And so based on looking at the notes, when you're asking me about a particular item, looking at the notes and seeing in which lane that item was put into the mini gel.
Now, incidentally, is this one of these x-rays or autorads that you had shown to the jury last week?
No. This is actually a photograph of this small gel, which is about two inches by three inches, and the gel is sort of opaque and you can see the edge of it right here (Indicating), this black--this was a full-size picture, that is, it had a lot of extra nothing out here, black, because this gel is laid on a light box, but instead of the white light that you see on the light boxes that have been used so far, it's an ultraviolet box. And because the DNA has been stained with a dye, if you were to look at this in color, the places where you see DNA sort of appear a pinkish orange and the gel has this sort of opaque look and then to--before it's put in the case folder, the gel is just trimmed out and the rest of the picture that doesn't contain a gel or anything else is just thrown away.
How do you read this particular photograph to determine approximately how much and what quality of DNA is present in a sample?
The photograph is--you can look at it and think about it just in exactly the same way that you think about the DNA on the autoradiograph. The DNA was put into a sample well up here and it moved down in this direction through the gel (Indicating), and these are three controls that are on the gel. This is the same lambda that's loaded on the large gel that we produced the x-ray film from. So this is a hundred nanograms of lambda and this is 50 and this is 25, and it has the same bands that you would see. And the reason this is on there is that we know the size of this top band is 23,000 base pairs; and what we're looking for is if DNA is in good condition, it will be up here because the pieces will be very, very large. As the DNA is more degraded, then you'll begin to see DNA down here (Indicating).
Because as it gets more degraded, the pieces are randomly broken up and all of the pieces get smaller and smaller and smaller. So you can see that the DNA in these lanes--and what you're looking at now is this--this--if you were looking at it on a light box, it would be coloration. Here it just appears white because this is a black and white picture. So you're looking at the distribution of the stain DNA from the top to the bottom of the gel. And if you see it all along, then you have some degradation here. To give you an example, this sample right here, whatever it happens to be (Indicating), does not appear to be very degraded at all. It looks very, very good.
Let's take the three, and I believe you described them all as lambda markers, the far right-hand three lanes that have a series of bands in each one?
They're controls just to say your gel ran as it should and to give us a sense of--of amounts of DNA, although this is not a real quantitative control. Some other laboratories use a cer--a known amount of human DNA in these positions instead of this lambda, and that actually works a little more nicely in terms of quantitation.
Let's go left to right if we can and let's just go to the first lane on the first left. Can you show us where that is?
Well, it looks pretty good. There's not a lot of it, but I see DNA here and I see a little bit of a smear coming down (Indicating), but it looks like it would be good enough to load on an RFLP gel.
In other words, from this result, in terms of the relative quality of the DNA, it appeared that an RFLP test might produce results?
And I believe last week, you described that from this evaluation or mini gel or yield gel--first of all, are those all terms used--
You described that it appeared that that would be enough DNA to be able to obtain a DN--I'm sorry--an RFLP result.
Yes. It certainly looked like it because you see there's a lot right here (Indicating).
And that turned out not to be true because of the condition of the DNA, that is what type of DNA itself it was; is that right?
It turned out not to be true, and we're now making a judgment call that it wasn't true because the DNA that we're seeing is not human. If this were human DNA, we would have seen a very nice RFLP pattern.
There's some DNA in this high molecular weight area. But you can see if you follow this down that there is some DNA that's all the way down in here (Indicating). So this sample is degraded. And if you only had this to look at--I mean now we know that it did give an RFLP pattern, but at the time that we looked at this, the assessment was it might, it might not. So we loaded it, but we didn't know if it would give us a result.
You have described earlier, and I believe as to three of the drops in this trail, that the DNA was very degraded when I asked you on the witness stand?
How would you characterize the result or the condition rather of the DNA with regard to 52, that blood drop in the driveway?
Okay. And since we're going to stick to the Bundy scene for the moment, what about the next lane over?
What you see here is that there is no DNA that's visible in this upper area (Indicating). So from that, you would assume that you are not going to get an RFLP pattern from this particular sample. You can see some DNA down here. See this smear that starts about--little more than halfway down and goes all to the--all the way to the bottom (Indicating). If that's human DNA, that's probably going to be good enough to give a PCR result.
And what result in terms of the presence of DNA can you determine from this particular test?
You can see a lot of DNA right at the top, a little bit of degradation in here (Indicating), but not a lot. And assuming that this is human DNA, you would expect that it would give you a very nice RFLP pattern.
Now, incidentally, before we move on, Dr. Cotton, this particular test, these--that ultimately you received the photographs from, this yield gel--I believe you used that term?
And these were all extractions that your laboratory did of DNA from the actual swatches sent to you from Los Angeles?
Okay. Now, could we move on to--what would be the next photograph, to go to the same page that's currently--
And does it show results as to any of these samples taken at the Bundy crime scene?
These are the same controls I just mentioned. 49 was in this lane and 50 was in this lane (Indicating).
Let's start--and again, first of all, were these samples run in your laboratory on a yield gel after your laboratory extracted DNA from these original swatches?
Both these samples are degraded to about the same extent. You have to look way down here at the bottom, and you see a smear of DNA here and you see a smear of DNA here and you see nothing up in this range here (Indicating). These two samples clearly are not good enough for RFLP testing.
Now, amongst these--first of all, have we now shown each of 47 through 50 and 52, each of the blood drops?
All right. Then perhaps, your Honor, we can remove or ask the witness to retake the stand and I'll ask her further questions.
Now, having shown these five samples, 47, 48, 49, 50 and 52, were you or can you summarize any differences in their relative amounts of DNA as revealed by these yield gels?
Your Honor, objection. Asked and answered. That was the question immediately before this.
You can get a general idea from the gels that the amounts of DNA are pretty much in the same ballpark with the exception of 56. But again, because this isn't a measure of human DNA, this isn't a very good place to try to get quantitation as to a precise amount.
Okay. Let's turn to human DNA then with regard to these samples. What can you describe about that?
Okay. Is there a way that you can describe those results for us from these various items, 47 through 50 and 52?
Okay. Can we address these in order? That might be easier to follow. For instance, item no. 47?
Oh, sorry. This quantitation is done from the PCR extraction, and the various amounts of DNA--what kind of answer are you looking for? Do you want nanograms or do you want like thoughts and not so much--
What would be the easiest way to describe any relative differences between these five drops?
Well, I can tell you which ones had the most, which had a middle amount and which had nothing that we could detect.
Okay. The samples that had the most DNA were 50 and item 52. The samples that had moderate amounts were 49 and 12, which I know wasn't--that's not on the--
And then the samples that had no detectable DNA on here, which doesn't mean they don't have any, but it just means we're not detecting it, would be 56--
I believe you described 49, 50 and 52 thus far. Can you describe for us 47 and 48?
Yes. 47 had no detectable, and for item 48, I think I have to go to another--I think I have to go to another film. Where can I find that? I have to go--I think I have to go to another film.
You described Los Angeles Police Department item no. 12, the Rockingham foyer, as having a moderate amount of DNA; is that right?
Before we move on to a different area, are these differences that you've described amongst 47 through 52 consistent or inconsistent with cross-crontom--I'm sorry--cross-contamination transfer of DNA as posed by Mr. Neufeld in his hypothetical?
Does the relative amounts--well, let me rephrase that. Do these results of the relative amounts of human DNA differ among these samples along the walkway drops?
Does that tell you anything or does that lead you to any opinions or conclusions about whether or not that DNA was transferred from other evidence items as opposed to being DNA collected in the locations as described?
Dr. Cotton, based on these differing levels of DNA in these various items, does that lead you to any opinion about whether or not the DNA detected in your testing is from material collected at a crime scene versus material transferred from stains during evidence processing?
It looks to me like--if it was a transfer, it would have had to been subsequently affected by the swatch it was transferred to. Otherwise, you have to--you have to postulate that it was--if it was a transfer, it wasn't from the same thing, it wasn't all from the same tube of blood or all from the same swatch because they're all different.
KEY QUOTENow, I'm going to shift topics, Dr. Cotton, if I could. You were asked a number of questions about packaging evidence items. Do you recall that?
Let's turn to plastic bags. Do plastic bags play any role in preventing cross-contamination?
You have one sample in a plastic bag and you have another sample in another plastic bag, it would be hard to get material from one sample onto the next sample.
When you discussed--and you were asked a few questions just this morning--may have been this afternoon, but I think it was this morning--about DNA, when you're talking about a bloodstain, is looking at or actually detects DNA that's contained in white blood cells; is that right?
You were also asked about some conventional serology techniques that type proteins such as--and I believe the slide actually had EAP on it; is that right?
Where does that protein obtain from in a bloodstain? Is it the white blood cells or something different?
In a bloodstain--and let's just take a bloodstain left at a crime scene--do the red blood cells go to some different location than the white blood cells or are they mixed?
In other words, are they all floating around until a piece of blood is deposited on a surface?
What happens to the cells at that point, once a bloodstain is--I'm sorry--a blood drop is left on a surface of any kind?
Well, let me focus it in a little bit if I can. Is it the case that those cells, white versus red, go to different locations in the blood stain or do they stay mixed?
The blood is a mixture of cells and proteins and other things. I think for most practical purposes, you can think of it as a homogenous mixture, so that when the blood is deposited, it would still stay a mixture. I mean cells are very tiny. You know, they're just going to be distributed in the bloodstain, white and red together.
Now, I'm going to shift your attention again to just briefly about evidence that you received from the Los Angeles Police Department. Did you receive any extracted DNA from the LAPD?
You received only evidence items themselves in the form of swatches, bloodstain swatches or unstained controls as well as known samples; is that right?
As far as all of the Los Angeles Police Department evidence items, were all of the extractions done in your laboratory that were received by your laboratory, the evidence items?
Now, I would like to turn your attention if I could to a particular control that was described earlier today in the course of your PCR testing wherein there were some detectable DNA types. Do you recall that?
And that's one of the controls you used to ensure that the test worked probably in a PCR test, right?
Can you tell us what evidence item number or numbers that particular control was a part of that same test?
Well, first of all, what item--okay. How many--yes, if you would. That's probably the best way.
Item 78, item 56, item 52, item 7, item 47, item 12. That control was started with those items. It was processed through with those items, and two of those items were also--two of those items didn't give any amplified product and were concentrated. After the concentration, one of them gave amplified product and the reagent blank gave two faint dots and the sample that was concentrated and then gave amplified product was item 56. And this morning, I think I was saying it was item 7, and that is not correct.
Now, these two faint dots that you've just described, did their existence affect the typing results of the items other than item no. 56?
In our judgment, they did not affect the typing results because--okay. Think of--you do the extraction and you start the control. You bring it along and you type the samples and you type the control. For those samples that typed at that point, the control did not show any faint dots. And, therefore, we interpreted those samples. So that was a judgment call on our part. Two of those samples were then--going forward now, two of those samples were then concentrated and one of them gave a type and the control gave two faint dots. They--so it isn't that you have a whole type and the control, but you do have two faint dots. We made a judgment to report those results because the dots in the reagent blank were faint. Now, whether we type that sample again at the point before it was concentrated--that is, when I say the sample, I'm now referring to item 56--is something I'd have to look up because I was getting confused this morning.
Okay. With regard to the earlier samples, that control showed no reactions whatsoever with DNA types; is that right?
At the first time that it was run, the controls showed no reaction. It did not show any reaction until it was put through the microconcentrator.
Okay. Let's talk about why in your view is it appropriate to type those, that is to report the results from all of those items that were a part of that control when that control showed some faint DNA detected when you concentrated it.
Let's take the worse scenario and assume that the contamination was in that control from the beginning and also in the sample from the beginning. If that contamination is so small as to not produce a typeable result of any kind, whether or not it's there, it can't have affected the results.
All right. As far as the later typing of item no. 56, why is it appropriate to report the results when it in fact showed that small or faint detectable level of DNA?
That's the question to give you the best answer. That's what I was confused on, whether or not we typed that sample again, and it might take me a minute to find that in the notes.
All right. Do you think it would take long or would you prefer to do it when you have more time?
With regard to the remainder of your tests, was there any DNA detected in any of the other controls?
In the positive controls, there was. But in the negative controls, there was no DNA depicted in any other negative control or any other reagent blank control run alongside any other sample that we did.
In other words, the remainder of the negative control showed nothing as far as controls not expected to show DNA?
Incidentally. You were shown a portion of your laboratory protocol today; is that right?
And I believe you were asked about a specific page that dealt with controls and decisions that are to be made based on, for instance, a negative control failing?
It's relatively vague. I mean, it's in the standard operating procedure, but I have to admit that that's a vague--basically--if you have any detectable DNA, you could say the control--I don't like this word "The control failed." If you have detectable DNA on that control, the control told you what you wanted it to tell you. It told you you might have a problem. It also may be telling you that you shouldn't interpret the results, that you should call them inconclusive, that you should do it again or you should think carefully before you give an interpretation.
As far as that control--and I believe you had started to describe earlier today about discretion in the laboratory; is that right?
On that particular page of your protocol, is there a provision giving Ph.D.s discretion to make certain decisions?
Yes. We always--I mean, you would certainly want to do that. There's no way you could write a standard operating procedure that could describe every circumstance for every test that you could ever get. So if you don't allow room to use your--your judgment in analysis, then you wouldn't be giving the best possible analysis.
Do you exercise that discretion as a result of your education, training and experience as a DNA analyst?
With regard to this particular re--negative control that showed this faint DNA present, did you utilize your discretion to determine that those results should be reported?
Incidentally, does your laboratory report results according to who's paying for your services?
In your laboratory, is there an approximate percentage of number of cases in which, for instance, suspects are excluded?
The approximate percent of cases in which we have an exclusion is about 30 percent.
It means that we've been asked to compare a victim or--let me back up. It means we've been asked to compare a known sample with an evidence sample. And if the known sample doesn't come from the evidence sample, then they are excluded as being a contributor. So depending on the nature of the evidence and the question that somebody else cares about, that's--can be an important piece of information.
Do you in your laboratory report results excluding certain suspects and report those results to Prosecutors who have asked you to do testing?
You have described, Dr. Cotton, the fact that in your laboratory, you don't test all genetic markers that are used in forensic science. And let's take an RFLP test for example. Is that right?
We use five. We feel that that provides for the great majority of cases a sufficient amount of information to--that additional markers would sort of be like icing on the cake. Now, there are circumstances where more is necessary, in which case you'd have to go to another lab to get more. But for the most part, five markers or if you did five markers and the PCR markers, you have a very good amount of information there.
For instance--and let's take item no. 52 as an example. How many total genetic markers on that Bundy driveway stain did your laboratory test at?
Dr. Cotton, if you could--and I'm going to shift to one other area briefly. Could you tell us what LAPD evidence item numbers your laboratory actually performed the extraction and then typing process on? Can you list those for us?
Exactly. Using--no. Actually extracted the DNA and then typed. In other words, you received an item of evidence, a swatch, and then extracted the DNA and then typed it.
I have in--I'm sorry. I have in total, but not by individual item number. If I could, your Honor.
The easiest way I guess for me to do that is to go through the report or to, you know, move through the reports to do that.
Item 49, item 50, the three blood exemplars which were labeled to us as c-1, c-2 and c-3, item 7, 12, 49--sorry--7, 12, 47, 52, 56, 78. I think I already said 49 and 50.
7. if I didn't already say 56, that's in there. If I didn't already say 48, which I think I did, that's in there.
Yes. And then the four unstained swatches, no. 7 control, no. 12 control, number 49 and number 46.
Your Honor, I'm going to repeat, if I may, in chronological order what I believe to be those numbers. Would that be acceptable to the Court?
And please stop me if I have any of these incorrectly, Dr. Cotton. The three knowns, c-1, c-2 and c-3?
Then items no. 7, 12, 47, 48, 49, 50, 52, 56, 78 and the four unstained controls, 7, 12, 49 and 56.
Now, if I may, Dr. Cotton, I would like to turn your attention to the area of population frequencies. All right?
Why is it that you can test and use in your databases, say, 4- to 600 people and yet be able to make statements about rarity of types that obviously are not only higher than 4- to 600, but are in the millions or even billions?
Objection. Twofold, your Honor. One, first, facts that are contrary to her testimony as to the size and, two, there's no foundation.
With regard to the number of individuals in your databases, approximately how many are there total?
You utilize those databases to create--not to create--to report population frequency data; is that right?
As far as these RFLP results, several of them are in the millions or even billions; is that right?
How can you take numbers of 4- to 5- to 600 of people in these databases and be able to determine estimates of frequency that are numbers higher than 5- or 600? Do you understand my question?
I do. Let me give you several different pieces to that answer. First of all, we are relying on work done by other scientists knowledgeable about RFLP alleles; that is, how many of them there are to give us some estimation, statistical estimation of how large a database is needed.
As to that, your Honor, I move to strike as to the hearsay representations of other people.
Secondly, the--keep in mind now it's impossible to test everyone and it is actually relatively time-consuming to even test 5- or 600 people given that you can get about 15 people on one gel. You can develop a sample size--a sample and make an estimate--make an estimation from that sample. And, again, the critical word here is "estimation." You could then go out and get another sample or another group to get another sample. And if this were a legitimate thing to be doing, you could say, does the distribution of frequencies, that is, how often I see a band at 5,000 and how often I see one at 6- and the whole distribution of how often you see a particular allele, does it look like other samples from the same racial group from another part of the country. It will not look the same, but it should look similar.
With regard to this process--and you've described now looking at--I'm sorry--at other information?
Some of the other information has come--well, it's come from various sources. There's information about our probes and our enzyme from a few sources in the United States, from many sources in Europe. There is information that's been compiled for the FB--by the FBI, a very large amount of information looking at a different restriction enzyme, but--and a panel of probes, several of which overlap with ours and several of which don't. The overall--
You've described the fact that you looked at other information. In particular, you were describing a study done by the FBI?
It looked at RFLP databases generated by various laboratories across the country and made comparisons as to the distribution of alleles from databases that were generated in various places at the various racial groups.
What's the significance of those findings as far as what I asked you about, taking databases and then making estimations that are in the millions or even billions?
What it tells you is that if you take a rac--a database from one part of the country for Caucasians, blacks or Hispanics and you compare it to a database from some other part of the country and you generated a profile frequency, that the frequencies are very, very similar. There are not large differences in the samples from one part of the country to the next.
You have described using RFLP typing at five probes, for instance, with regard to the Bundy stain, no. 52, and the boot drop, no. 78?
When you make these estimations of frequency--and I believe you touched a little bit on a concept called independence?
It means whether or not you inherit one allele that you have is not--does not affect the second allele that you might get. That is, if you inherit a band at 5,000 base pairs, that doesn't mean you'll automatically or with some probability inherit on at 6,000. What you inherit from one parent is what you inherit from the other.
Mathematically that's important because if that were not the case, it would be improper to multiply the frequencies between the different genetic locations.
How do you--well, first of all, are these markers independent that you've described in your testing in this case?
We've gone beyond. We've already covered this once before. I know it was not directly touched upon in cross-examination.
Do you need a database for each community of the United States to be able to estimate these frequencies?
Do those include, for instance, these studies that you've described of groups of people in different parts of the United States and the world?
When you say the material that you have--I'm sorry. When you say specifically for the reasons that you give earlier--given earlier, can you tell us briefly what those reasons were?
These frequencies that you've reported in this case, are they accurate in terms of being precise or are they estimates?
These numbers that you've reported, do they tell anything or do they have any relation whatsoever to the facts of this case? And I'm talking about the facts other than DNA.
Are they estimations only of what--of how common or how rare the various DNA types are that you obtained in your testing in your lab for all of the samples that you've described in your testimony?
They are only estimates, which give you a conceptualization of how common or rare the collection of genetic markers is.
Do they in any manner take into account at all all of the other facts of this case that show what happened in this case?
They don't take into account anything except saying is this collection of genetic types common or rare or somewhere in between. That is the only thing that those numbers tell you. They tell you nothing else.
All right. Your Honor, with the exception of the one area the witness asked to have a little time to look up, I'm concluded with my redirect at this time.
There are no false positives and no incorrect exclusions in the remainder of those samples since 1989.
47, 48, 49 and 50 are consistent in type with Mr. Simpson. 56 is consistent in type with Nicole Brown. So if all of those samples were contaminated, they couldn't have all been contaminated from the same source.
It looks to me like--if it was a transfer, it would have had to been subsequently affected by the swatch it was transferred to. Otherwise, you have to postulate that it was--if it was a transfer, it wasn't from the same thing, it wasn't all from the same tube of blood or all from the same swatch because they're all different.
Let your conscience be your guide.
That reagent blank control was started with those items... this morning, I think I was saying it was item 7, and that is not correct.