Dr. Cotton, are you familiar with the issue that the Court has framed and wishes you to address?
All right. With respect to in particular item no. 78, the bottom of Mr. Goldman's shoe, did you perform RFLP typing on that particular sample that was provided to your laboratory?
The best indication from the banding pattern that it is a mixture is that the intensities of the bands in the pattern are different and there are more than eight bands in the cocktail. And in the individual probes there is at least one probe where you see three, so the total number of bands and the differing intensities of the bands confirms that in fact you have more than two people there.
Your Honor, with the Court's permission could we illustrate that by use of the overhead projector?
I believe that would have been my next exhibit anyway. Shall we just go ahead and mark that as the People's next in order?
All right. People's 257, but remark it in front of the jury so that they are aware of it.
In fact, I think we may have discussed this yesterday in terms of marking the exhibits, with respect to this particular autorad there is what the witness has just described as a "cocktail," and then there are associated autorads that basically look at the individual loci one at a time, so would the Court like that, for instance, marked 257 a through whatever? I think that might be easier.
All right. If it is associated to the same test, I would assume that would be the most logical way to do it.
All right. Dr. Cotton, with regard to this particular test, that involved item no. 78?
Did it involve any other test samples, that is, evidence samples in this case, other than known samples?
With respect to those autorads, would it be appropriate to begin with what has been referred to as the cocktail autorad?
And then with respect to the remaining autorads, do they then represent individual loci or individual genetic markers typed one at a time?
Are there names for each of those markers? Perhaps we can--would the Court like the witness to describe what marker will be b and which marker c and so forth at this point?
Would it be appropriate to mark the first individual genetic marker test, ms1, as the letter b?
Would it be appropriate to mark as next in order that autorad that deals with the probe ms-31?
Yes, but there are two of them and you might want to distinguish--distinguish them by their development date.
All right. And with respect to the second autorad dealing with this genetic ms-31, what date is it?
With regard to e, would it be appropriate that that be the particular genetic marker that is the autorad resulting from the test of the genetic marker ms-43?
Are these letters and numbers simply designations for these different genetic markers?
All right. Then with the Court's permission what I'm going to ask the witness to do is, first of all, to look at these autorads in the order that they have been marked by projecting them on the elmo machine and then having the Court--I'm sorry, having the witness describe item 78 and its results.
Counsel, for the purposes of this hearing, what I'm interested in is how do we determine that it is a mixture and then my next question is once I come to the conclusion that there is a scientific basis for determining that there is a mixture, the next thing I'm interested in is why shouldn't I require a statistical analysis or statistical significance factor attached to that conclusion that the party--relevant parties aren't excluded based upon the comments of the NRC at page 59?
Your Honor, just to save time, we will stipulate that it is a mixture so you can get right on to the second issue if you want.
All right. Dr. Cotton, could you start with the cocktail then, exhibit 257-A, I believe.
All right. Then with the Court's permission then could the witness come down so that she can view the projector screen and if necessary use the point maker?
Now, Dr. Cotton, without getting into detail about exactly what is on this autorad in terms of items other than 78 and the known samples, is this the particular autorad that would have been the first one developed in your examination using RFLP typing of item 78?
Now, as far as the--as the results that are shown there, do they demonstrate the existence of a mixture?
If you count up the number of bands, if I remember correctly in this cocktail there are eleven. The cocktail is a group of four probes, so if you expect to see two bands maximum with each of four--with each probe, then for a single person with a group of four you would expect to see eight.
Yes. You can see that the lower three bands are much different in intensity than the upper bands--than the band above them and that is the second clear indication that you have a mixture there.
Now, with regard to this initial autoradiograph, and you have described how you are able to determine a mixture, were you able to make any comparisons with known individuals who are also shown on this autorad?
There were--essentially you are making comparisons with all the known individuals on the autorad and two of the known individuals on the autorad are consistent with being contributors to item 78.
Now, with respect to these--and you have identified three lower bands as being less in intensity than the remaining bands?
Are those, based on this initial autorad, and I'm referring to the three bands, the three less intense bands, are they attributable to one person or the other?
Are they consistent or inconsistent, that is, the three bands again, with Nicole Brown?
Based on this first test or first typing process, using this RFLP method, what conclusions were you then able to reach?
For that sample, the conclusion would be that you do have two people there and the possible contributors from the known individuals that we have would be the major amount of DNA coming from or consistent with Nicole Brown, and the minor amount of DNA consistent with some of the bands in Mr. Goldman's pattern. There are not all of his bands there in this cocktail; there are only three.
Is this feature of difference in intensity something that you have experienced in the past in your case work?
All right. First of all, while the cocktail autorad, 257-A is on the projector, are there any further features about this autorad that are significant as far as determining the existence of this mixture and who may or may not have contributed to it?
All right. Mr. Clark, at this point I'm persuaded that there is a scientific basis for determining the mixtures here and from what I have learned so far there is a basis to determine that there is an ability to differentiate contributors.
Okay. Actually, perhaps I can do it in just a very short form by asking the witness.
With respect to the remaining autorads that deal with these genetic markers individually, what information, that is what further information, if any, did they provide you in interpreting the existence of this mixture and who may or may not have been a contributor to it?
In using the individual films, there is a small additional amount of information. One is on the ms-1 film there are four bands seen. Two are consistent with Nicole Brown and two are consistent with Mr. Goldman, and one of those bands that is seen on that film is not visible on this cocktail. That brings the total number of bands consistent with Mr. Goldman to four and that is the total number of bands through all the testing on 78 that were consistent with Mr. Goldman. There is--I think if I remember correctly, one other piece of information on one of the other probes where you can--you see again one of the three bands that you saw initially and that may be the g-3 probe, although I would have to check to be sure, so you can identify one of the three bands from the cocktail as coming from a specific probe, one of them coming from ms1, one from another one, I think it is g-3. That leaves you a third band on that cocktail that you can't identify which probe it came from and it adds the ms1 individual film, adds a fourth band, giving you a partial pattern of a second person.
Mr. Clarke, let me interrupt you. Mr. Shuman, what article are you reading right now?
All right. I seem to see a picture of the Defendant as you turned it over; is that correct?
All right. Dr. Cotton, with respect to this mixture as you have described it, you ultimately rendered conclusions about item no. 78 that you placed in your report; is that right?
We reported that the DNA banding pattern--that the DNA banding pattern from item 78 consisted of two separate patterns. One matches Nicole Brown and there are four bands remaining. Those four bands match four of Mr. Goldman's pattern. And that Mr. Goldman could not be included or definitively included or definitively excluded as the donor of those additional four bands.
With respect to the match between eight of the bands on item 78 and Nicole Brown, did you report a frequency to describe approximately how common or how rare those characteristics shared by item 78, that is, those eight bands and Miss Brown were?
Did you also report an approximation of the frequencies of the characteristics shared by the additional four bands with Mr. Goldman?
Because we only had four bands and clearly do not have a complete banding pattern, then the result is basically inconclusive with regard to Mr. Goldman, and we get that based on our opinion that the result was inconclusive. An additional frequency for those bands would not be necessary--we wouldn't normally do that.
Would it be, in your opinion, appropriate to report frequencies for those four additional bands that could have come from Mr. Goldman?
There is nothing wrong with doing it. It--it, however, in my opinion, regardless of whether or not you attach a frequency to those four bands, it is still an inconclusive result and therefore attaching that frequency seems somewhat non-helpful.
We made a usual frequency calculation for all of the bands that are consistent with her using the frequencies for each band for each probe in the usual multiplication manner.
The Court addressed and you probably heard the Court address the NRC report and calculating frequency data?
With regard to the NRC report and its discussion of population frequency data, what does it say about calculating frequencies for a situation like Mr. Goldman's four-banded pattern?
Mr. Clarke, I didn't read that overnight, so I can't tell you exactly what it says.
Okay. With respect to this type of reporting, in other words, should a frequency in your view be reported for this material? You have described how you didn't do that. You have described also the fact that it can be done. Let's shift your attention to PCR testing. First of all, was PCR typing conducted on material from this same stain?
With what type of results? Without getting into the actual numbers for each genetic marker, can you tell us what those results revealed?
Umm, if I am remembering correctly, for at least one of the markers there are three alleles and again get more than two, there you have a strong indication you have a second person.
With regard to those then, in that mixture were you able to determine whether or not individuals in this case, that is the known samples, any of them could be excluded or included?
The results are basically the same as the RFLP, that Nicole Brown and Mr. Goldman can be included; Mr. Simpson is excluded.
KEY QUOTEAs far as these individuals and their ability to be included, what about assigning population frequency estimates to that? How do you feel about that?
We didn't assign any population frequency estimates to that. The signals on the dot-blot are not sufficiently differentiated that you can say these two alleles must be from the major contributor and these--and this other one or two from the minor contributor. You can't really tell this apart on the PCR result, so we didn't attach any frequency to the result at all.
So there was a different situation than the RFLP results where there was clearly a difference in intensity?
As far as these results, and let's take them in total now, the RFLP results as well as the PCR-based results, do they provide you any additional information about whether or not it would be appropriate to basically sum up frequencies to describe the significance of these mixtures or these alleles contained in these mixtures?
Actually, it is a little easier, I think to think about them separately as opposed to together.
The PCR mixture, the signals indicate there is a mixture, but it is not--you can't differentiate one contributor from the other. In that case it would not be inappropriate to basically take--do a calculation that says what's the sum of every possible contributor to this mixture. On the RFLP results, however, the signals are so well differentiated and that I think it would be very much understating the strength of the data to do that type of calculation for the RFLP result.
Would it be understating it not to provide any frequencies to describe these mixtures or this mixture?
I don't see any reason not to provide a frequency for the bands that are consistent with Nicole Brown, that they are so much more intense than the four additional bands. I don't see that calculating a frequency for those four additional bands adds a lot. That is just my opinion.
The results are basically the same as the RFLP, that Nicole Brown and Mr. Goldman can be included; Mr. Simpson is excluded.
Here we have eleven. You can see that the lower three bands are much different in intensity than the upper bands — that is the second clear indication that you have a mixture there.
Regardless of whether or not you attach a frequency to those four bands, it is still an inconclusive result and therefore attaching that frequency seems somewhat non-helpful.
I think it would be very much understating the strength of the data to do that type of calculation for the RFLP result.