All right. Dr. Cotton, why don't you retake the witness stand. All right. Thank you, ladies and gentlemen. Please be seated. All right. Let the record reflect we've been rejoined by all the members of our jury panel. Mr. Neufeld.
Thank you. Good afternoon again, ladies and gentlemen.
THE JURY: Good afternoon.
RECROSS-EXAMINATION MR. NEUFELD
Dr. Cotton, on redirect examination, Mr. Clarke asked you a series of questions concerning relative degradations if you will of the different items or some of the different items involved in this case that Cellmark analyzed. Do you recall that?
And along with the drops purportedly collected at Bundy, he also asked you about the--about item 78 and item 56. Do you recall that?
Now, and I think you said as to item 78, that there seemed to be a fair amount of high molecular weight DNA present; is that correct?
All right. And--and these questions that were put to you by Mr. Clarke were put to you in the context of showing the range of degradation that occurred on these different samples. Do you recall that?
Now, are you aware, Dr. Cotton, of the fact that item 78 wasn't even processed by LAPD on either June 13th or June 14th?
Would you agree as an expert that if in fact--in fact item 78, as a collected swatch, didn't even arrive at the Los Angeles Police Department on the days when they were initially processing these items, would that change your opinion as to the--as to the consequences of the variety of degradation on these samples?
Well, if it wasn't processed at the same time, then all the various hypotheticals about--that I was discussing wouldn't be applicable because it wasn't even there.
KEY QUOTEAnd also, you were asked about item 56. And, Dr. Cotton, were you aware of the fact that when extractions of DNA samples were done at LAPD on the 14th, that item 56 was not included in that group?
Dr. Cotton, again, just as I asked you with regard to item 78, assume hypothetically that item 56 was--did not go through the extraction or the processing procedures for DNA typing that the Bundy drops went through on the morning of the 14th. Again, would you draw that same distinction, that those hypotheticals wouldn't apply?
I think the one thing that you did say on redirect examination is that all those samples that purportedly originate from the Bundy walkway were either very degraded or moderately degraded; is that correct?
And you had mentioned by the way that--I'm sorry. Withdrawn. On cross-examination, initially, you did say that the one table that you could rely on in the NRC report was the table 1-1, which dealt with the DNA content of biological samples. Do you recall that?
And would you agree, Dr. Cotton, that in that table in the NRC report, it states that the amount of DNA present in a milliliter of blood is somewhere between 20--
The question has to be directed toward the amount of DNA present in degraded samples. That was what was asked on the redirect.
--Dr. Cotton, that there are approximately 20,000 to 40,000 nanograms of DNA in a milliliter of blood?
And are you aware, Dr. Cotton, that there are approximately 20 drops of blood in a milliliter of blood?
Well, are you--are you--would you agree that as a rough estimate, that there are approximately 20 drops of blood in a milliliter of blood?
I don't really--I don't really know. And when you're--when you're using something, the--the opening of that instrument, like you have a pipetter tip with a big opening versus a little opening, you have different size drops. So I would rather work in some other quantitative sense than--than drops.
Have you reviewed any literature which suggested that there were approximately 20 drops of blood in a milliliter of blood?
Can you estimate based on your own experience approximately how many nanograms of blood--excuse me--how many nanograms of DNA are in a drop of blood, an average drop of blood?
I don't think I can give you a range given that I'm--what I'm telling you is that I don't really know what the volume is in a drop and, therefore, I'm hesitant to try to carry that any further.
All right. Dr. Cotton, but you would agree that at least as to all these samples from the Bundy walkway, they are either experienced moderate or extreme degrees of degradation; is that right?
And you can not tell, Dr. Cotton, when you look at the yield gel or the slot blot as to whether the degraded or the remaining DNA that you see is there because it's from the original source or it's there as a result of cross-contamination; isn't that correct?
I believe you also said, Dr. Cotton, that the role that the plastic bags play in preventing cross-contamination is that obviously if a sample is in one plastic bag and another sample is in a second plastic bag, that they're not going to cross-contaminate while in that status; is that right?
But would you agree, Dr. Cotton, that once the samples are removed from the plastic bags, the plastic bags are no longer a deterrent to cross-contamination? Isn't that right?
And, Dr. Cotton, when you're referring to the reagent blank control, lighting up two DNA dots in this particular case, I believe you said that there's some discretion left to the Ph.D.s in the laboratory to decide whether or not to retest; is that correct?
Isn't it a fact, Dr. Cotton, that the protocol states that when the results--I'm sorry--that when a questionable result is reported, that it's to be interpreted by the Ph.D.s in the laboratory?
And would you agree, Dr. Cotton, that with respect to the presence of those two dots, those two DNA dots on the reagent blank, their presence on those reagent blanks was not questioned?
No. It's obviously there. I mean it was recorded by the analyst who read the strips. And if I remember correctly, you can just barely see it in the photos, but you can see it. So it's clearly there.
And, Dr. Cotton, you were also talking about how your database has approximately 600 people in it; is that correct?
If you add up all the three racial groups--you know, taking into account you don't have the same number of people in each probe, it's I think between 5- and 600.
And your database includes five different genetic loci, is that right, for the RFLPs?
I asked you, if you recall, on cross-examination initially if you could find out for us as to how many people in that African American database you actually ran all five genetic markers on. Do you recall me asking that question?
And, Dr. Cotton, how many members of your African American database have been subjected to all five genetic loci in this case?
Two people in the entire African-American database have been subjected to all five loci in your laboratory; is that right?
Okay. Dr. Cotton, you gave an answer before on the subject of--of the assumption of independence of these different genetic traits. Do you recall that?
And would you agree, Dr. Cotton, that that issue, okay, as to that assumption of independence is a question that arises in the or was in the province of population geneticists?
And, Dr. Cotton, do you consider yourself an expert in the field of population genetics?
No. I'm certainly not an academics expert in the field of population genetics. I know a lot about it as it pertains to forensic DNA typing, but there's much more to know beyond what I know.
KEY QUOTEAnd, Dr. Cotton, you said at the very close of the redirect examination that these statistics that you put up on the board only tell you about the rarity of a particular profile; is that correct?
And so would you agree, Dr. Cotton, that those statistics tell you nothing about the probability of a false positive at LAPD?
Well, if it wasn't processed at the same time, then all the various hypotheticals about--that I was discussing wouldn't be applicable because it wasn't even there.
Yes. Of all the blacks, there are only two that are across all five.
No. I'm certainly not an academics expert in the field of population genetics. I know a lot about it as it pertains to forensic DNA typing, but there's much more to know beyond what I know.
Yes. Of course that's right.