Dr. Cotton, as a rule at Cellmark diagnostics when you receive samples to do DNA testing you are limiting your assessment of the evidence to the--to the DNA itself; is that correct?
And you are there to basically to do two things: One, determine whether bands are present, or dots, in the case of PCR typing, and two, if they are present, to estimate the frequency or rareness of that particular pattern; is that correct?
Well, I mean you are not supposed to have any of the biases or other influences that, say, detectives working on the case would have? You are simply looking at it in a purely scientific fashion; isn't that right?
And when you look at the--and when you give your estimation of what the data says, you are to do that in a way that is not biased or influenced by other non-scientific evidence in the case; isn't that right?
All right. Well, your Honor, I believe actually it will be helpful to you because it will give you a context in which to understand her impression of the autorad.
Counsel, I understand completely the context. I want to know why this is your motion to require the Prosecution to provide statistical significance, calculations for the mixtures. That is all I'm interested in.
Now, one of the things that you were talking about before under Mr. Clark's questioning was the disparity in the intensity of certain bands as an indication of possible different sources; is that correct?
All right. Would you agree, when you look at the bands, first of all, on item 78, that if we count from the top there is a--it is difficult do see on the overhead, your Honor, but beneath the first band are there two bands very, very close together?
I don't think it looks like a single large blob. It looks like a--do you want me to use the pointer thing?
Please do. That will be great. Or at least point out the two bands that I'm referring to.
And the upper one is less intense than the lower one and a little bit less intense than the very top one.
Okay. Did you make a determination as to that--the less intense band of the two bands that are very close together, whether that is consistent--consistent with bands for Nicole Brown Simpson or for Ronald Goldman?
I believe on the--using the individual probes following the cocktail, that this band is consistent with Nicole Brown.
Okay. And, umm, would you agree that that light band is considerably less intense than the band directly beneath it?
No, I don't think so. We are talking about this darker one right here, (Indicating).
Okay. Now, would you agree that there is differing intensity between the band that you just described as being above that band in item 78's lane and some of the other bands that you attribute to Nicole Brown Simpson or you say are consistent with Nicole Brown Simpson?
Okay. So in other words, even within the same individual, you can observe on this lane bands of differing intensities; isn't that correct?
And again, if you go down to the next band, that is a band that you believe was consistent or in the same position as bands in the Nicole Brown Simpson's lane?
And then you go down one more and that is another band that you believe is consistent with Nicole Brown Simpson?
New and would you agree that that band that is attributable to Nicole Brown Simpson or say is Nicole Brown Simpson also has a differing intensity other than bands that you say are consistent with her profile?
It looks slightly different up here, (Indicating). If you want me to give you the best judgment, I might want to look at it here on the light box for just a second.
I would be happy to look at the copy as opposed to taking the original off the thing.
And so now that you have had a chance to look at it on the light box, Dr. Cotton, would you agree that that other band which I just called your attention to which you say is consistent with bands coming from Nicole Brown Simpson, that that, too, is less intense than bands above and beneath it which you will say are consistent with Nicole Brown Simpson?
Okay. And now also while you are there, could you take a look at the lane next to it, item 52.
Item 52 is one of the drops at Bundy. In fact, it is the drop that is closest to the alleyway, your Honor.
And item 52 and the banding pattern you believe represents DNA donated by one person; is that correct?
And would you agree that even though you say it is from one person, that as far as band intensity goes, that the bands--that the three bands--the first three bands at the top are considerably fainter than the three lower bands?
What it has to do with the mixture is one of the criteria that this witness was using to try and disaggregate the picture and give therefore a frequency for a complete profile as opposed to using the NRC method of aggregating those frequencies, was her opinion that you can rely on the fact that there is a differing intensity in the bands.
She said it, but what I'm saying is that the evidence here belies that position as a criteria for making that distinction in a scientific fashion. That is the point.
KEY QUOTEAll right. Well, there is a sentence in the NRC report which says that: "if a suspect's"--and I quote--"if a suspect's pattern is found within the mixed pattern, the appropriate frequency to assign such a match is the sum of the frequencies of automatic genotypes that are contained within the mixed pattern," unquote. All right?
No. 1, have you ever seen any scientific publication which contradicted that approach to aggregating genotypes for mixed stains?
I don't recall seeing a specific scientific publication that has addressed that issue, other than the NRC report.
KEY QUOTESo I take it then your answer is there is no scientific literature that you are aware of that would contradict--
And one last thing, Dr. Cotton. Just so I'm clear on this, by your own remarks in response to Mr. Clarke's questions, what you are saying is that as to the PCR profiles, though, you would agree that the appropriate approach is to aggregate those genotype frequencies?
If one is going to put a number associated with that data, then that would be the appropriate approach.
KEY QUOTEI am just--she said it, but what I'm saying is that the evidence here belies that position as a criteria for making that distinction in a scientific fashion. That is the point.
I don't recall seeing a specific scientific publication that has addressed that issue, other than the NRC report.
If one is going to put a number associated with that data, then that would be the appropriate approach.
I want to know why this is your motion to require the Prosecution to provide statistical significance, calculations for the mixtures. That is all I'm interested in.