All right. Thank you, ladies and gentlemen. Please be seated. Dr. Gerdes. All right. Let the record reflect we've been rejoined by all the members of our jury panel. Dr. John Gerdes is again on the witness stand undergoing recross-examination by Mr. Clarke, who is about to conclude his recross-examination.
Dr. Gerdes, just returning, if I could for a few moments, to the area of different levels of DNA in samples. You've described age as a factor that can impact how degraded a DNA sample is, correct?
Whether the sample is collected in a relatively wetter or drier state impacts that rate of degradation?
So those are a series or at least five or six, four or five or six examples of factors that can affect how a sample degrades and at what rate?
Now, you've described, Dr. Gerdes, your opinion that 28 percent of the time, that there was a contaminant in your examination of the LAPD PCR typing that was not shown in the negative control?
Now, that is dependent on how you've used the term "Contaminant" through all of your review of that material, correct?
That includes dots or reactions from the various types that are less than the C dot, correct?
And, in fact, from your review of the LAPD, that includes a very large number of samples that in fact had reactions that you classified as a contaminant that were less than the C dot, correct?
It's important in interpreting a single sample known to be from a known individual.
Is there any instance in this case in which a dot is called as a genuine result where it's less than the C dot?
I don't recall. I think there are some that are very close in terms of my interpretation versus theirs and from looking at the strips.
In this case, as to the results--and I'm sorry. Your answer is, you don't recall, but you think there may have been?
As far as samples that are called, again, in this case, isn't the fact that reactions are at the C dot or higher very important in determining the accuracy of results?
Well, I'm sorry, Dr. Gerdes. What my question is to you is, isn't it a fact in calling results in this case, whether those results are at or above the C dot is in fact very important in calling DQ-Alpha results?
It's what the package insert, that little insert that comes with the kits recommends also, isn't it?
It's what Robin Cotton and Paula Yates and Julie Cooper followed in this case, correct?
As far as these kits from Roche, you don't have any complaints with Roche about the quality of the kits they manufacture, do you?
And, in fact, you use your own kit for--well, let me rephrase that. You use the Roche manufactured kit to test chlamydia in clinical casework, correct?
Now, earlier, you described the fact that in your opinion, contamination at the LAPD was predominately in the reagent extraction controls. Do you recall that?
And you used the term "At early stages," that is at early stages in the DNA typing process; is that right?
Where is that shown--let me rephrase that. As far as contamination shown in the early phases or early stages in this case, where is that shown in the controls that were run in this case?
The two reference samples showed evidence of cross-contamination. Other than that, the other controls were clean.
Aren't the fact that those controls all operated properly, isn't that extremely an important fact in evaluating the reliability of the results in this case?
In this particular case, you're dealing with very degraded samples and with low levels of DNA. It introduces a new situation in terms of how well those controls would be expected to work as we discussed on direct exam.
But again, isn't the evaluation of all those controls central to interpreting the accuracy of results using any PCR marker?
Now, what you've described earlier this afternoon as substantial errors at the LAPD, was that in reference to the five errors that you allege the LAPD made in typing?
So that wasn't--your comment about substantial errors wasn't related to anything other than those five alleged errors that were discussed during cross-examination as well, correct?
I was referring to the five errors and the fact they have substantial contamination that persists.
Until this problem is solved in terms of getting a handle on working with these types of specimens and the difficulties of the cross-contamination and other kinds of contamination problems, that's my opinion, yes.
KEY QUOTEAnd, Dr. Gerdes, the opinion you offer about PCR and the fact that in your opinion, it shouldn't be used, you offer that opinion whether or not there are RFLP results based on the same sample?
Dr. Gerdes, Mr. Clarke asked you if there were tests that you performed in this case to confirm a hypothesis of cross-contamination. Do you recall that?
If the Rockingham glove and Bundy blood drops were cross-contaminated in the evidence processing room on June 14th, is there any kind of a test that you can think of that can prove that now?
No. At this point, it's essentially the same DNA. It's been transferred physically, and from that point on, there's nothing you can do, any kind of analysis that would allow you to determine that that's the reason that that DNA is on that sample.
KEY QUOTEHe asked you questions about tests to determine levels of bacterial degradation. Do you recall that?
The--you were asked questions about the bloodstains on the back gate that were collected on July 3rd versus the Bundy blood drops that were collected on June 13th. Do you recall those?
Now, is it your understanding that all those samples were originally dry when collected?
And if you put once--whether wet or dry, if you swatch the sample with a wet swatch--
And in terms of these stains on the back gate--you've read the demonstration papers in regard to the effects of environmental conditions?
I don't--I'm not convinced they're rigorous, but they deal with the kinds of things that possibly could cause degradation.
But in terms of their demonstrations, do they demonstrate that sunlight on a bloodstain over time causes degradation?
Does it indicate that exposure to moisture and other environmental insults over time on a bloodstain causes degradation?
In terms of your microbiology background, would you expect that there would be degradation on stains over time that were exposed to sunlight, moisture and other environmental insults?
Were--in terms of location, were samples 50 and 117 separated by more than a few feet?
Now, you were asked a whole series of questions about the relevance of the C dot. What is your opinion about the relevance of the C dot when interpreting mixtures?
Well, in terms of a control, when interpreting a DQ-Alpha strip with a mixed sample--withdrawn. Mr. Clarke asked you questions about the C dot being a very important control. Do you recall those?
And your answer was, it's an important control when you're dealing with a known--one known sample, correct?
All right. When dealing with a mixture, what is the relevance of the C dot as a control?
It simply states that there's enough DNA there to type, but when there's a mixture, you can't interpret how much of that DNA is from the first contributor or individual and how much is from the second. And so the intensity of the dots become irrelevant.
So the intensity--when you're dealing with the mixture, the intensity of dots relative to the C dot, what is the relevance of that in your opinion?
Now--and in the user guide, do they say in a mixture, that you should interpret that the same way you interpret a single source sample in relation to the C dot?
No. They state you should be extremely cautious when you are dealing with mixtures or--
Without bringing the boards back up again, with respect to the 1.3 dots, the faint 1.3 dots on the Bronco sample, on item 31, and the 1.3 dots on LAPD item 52, does development time as illustrated by those boards, is that a factor in terms of the intensity of the dots?
What about the controls in those samples? What is the purpose of a positive control when running a series of experiments like that?
Well, if you have any indication of dots or human DNA or artifacts that shouldn't be there, you can't--you should not interpret that result.
If the controls fail, is it scientifically correct in any kind of scientific experiment to call the results?
1315 and 1316. Well, actually, your Honor, maybe we can make the first one 1315-A and the other one 1315-B.
Now, Mr. Clarke handed you some typing sheets from casework that you had never seen before?
No. Well, I may have seen them while I was at the laboratory. I didn't have them in my documents here.
No. I know. I may have seen them at or looked--glanced at them while I was at the laboratory. They were not a document that I requested on discovery. It was not provided to me to look at at a later time.
Now, this is Defendant's 1295. Do those two pieces of paper that Mr. Clarke showed you in any way change your opinion about the level of contamination that you found on runs at the Los Angeles Police Department between May of 1993 and August of 1994?
No, they don't. Those were all evidence items and they weren't something I would have considered in the analysis.
These are two pages that were just provided on discovery. One was discovered with the first batch of discovery and the second was subsequently provided again at a different date.
It shows a series of strips and then some of the strips, 1 through 4, have been blocked off. At that time, a number of strips were blocked off like this, and it was explained to me that this is because they were evidence items.
KEY QUOTEThis is the same page on a subsequent discovery when--this time, they're not blocked off and the first item is a control swatch.
Were you dependent upon what was provided to you in terms of the materials about what you got from the LAPD people when you made your request?
Dr. Gerdes, with regard to that particular set of samples that you just placed on the board, that involved a control, correct?
And, in fact, on your chart, you note that control as having what you characterize as a contaminant, correct?
I believe so, yes. Well, actually that was--that particular item was mailed to me before that, sometime in December.
So you've had that sample with all of the samples shown for at least seven months?
And, in fact, both of the charts that you provided to the People both show that particular sample as one of your alleged instances of contamination, correct?
Yes. The point is that it was blocked off the first time I received it and only through discovery being able to see all of the unblocked off materials--
Dr. Gerdes, what I'm asking you is, didn't you have an opportunity to see that at least seven months ago?
And, in fact, you got to see all of the strips that were in the binders at the LAPD, correct, DQ-Alpha strips?
You had an opportunity to see the polymarker strips, but elected not to review them; is that right?
Now, as far as item no. 117, Dr. Gerdes, you don't know how much was in that sample when it was left there, do you, how much DNA?
According to the check gel, the yield gel, it's not degraded to the degree that the others are.
Now, with respect to items 47 through 50 and 52, they were stored in plastic bags, correct?
And, in fact, they were in a wet state while they were stored in those plastic bags in a truck, correct?
I'd--a lot of those details are--I'm not aware of the details on that second set--that second time they did this.
I'd like you to assume hypothetically that when 115, 116 and 117 were collected, they were placed in plastic bags and, in fact, they were recovered from those plastic bags at a time much less than was the case with the Bundy blood drops.
As far as the time that samples may spend in plastic bags when they're collected, wouldn't it be a factor how many evidence items were collected at the same time, whether it's one or two others or whether it's perhaps 30, 40--30 or 40 other stains. Would that be important in terms of how much time that wet blood spent in a plastic bag?
If I understand your question correctly, you're asking me if it would make a difference if there was one swatch or 50 swatches in the same plastic bag, is that what you're saying, as opposed to all in different bags?
No. The actual collection of a number of items so that the evidence collector would have to spend more time in the collection process.
Would you agree that the less time that a particular item spent in a plastic bag in a wet state, the more likely that sample would contain more DNA?
Would you agree that, in fact, that could account for in this case the difference in DNA amounts in 117 versus 47 through 50 and 52?
As far as these number of factors that can account for differences in DNA levels, you would agree, would you not, that the time spent in those bags would be an important factor?
Showing you what's 1165. Mr. Clarke has been asking you if you know the amount of blood to start with on 47, 48, 50, 52, 115, 116, 117, right?
Now, in terms of the amounts of high molecular weight DNA, there's 1165 based on a hypothetical chart, subsequently the bar chart. Does that reflect the comparative amounts of high molecular weight human DNA in the Bundy blood drops as opposed to 117?
Showing 1192-A and B. Let's start with A. Do you recall seeing this chart introduced through the testimony of Gary Sims indicating a comparison of the concentration of 117 compared to the other samples?
Do you know--you were asked about when these bloodstains were deposited on these locations, correct?
No. At this point, it's essentially the same DNA. It's been transferred physically, and from that point on, there's nothing you can do, any kind of analysis that would allow you to determine that that's the reason that that DNA is on that sample.
It's irrelevant.
Until this problem is solved in terms of getting a handle on working with these types of specimens and the difficulties of the cross-contamination and other kinds of contamination problems, that's my opinion, yes.
Nobody knows.
It shows a series of strips and then some of the strips, 1 through 4, have been blocked off... This time, they're not blocked off and the first item is a control swatch... It's contaminated with a 4 dot.