Thank you, ladies and gentlemen. Please be seated. Dr. Cotton, would you resume the witness stand. All the jurors have now rejoined us. And as I recollect, we were just talking about the designation of the exemplars by letter.
So again, Dr. Cotton, as far as your laboratory was concerned at the time of testing, the identities of the persons from whom those three blood samples came from, known samples were basically unknown to your laboratory?
Now, after receiving various pieces of evidence in this case, was testing conducted on them using various DNA typing approaches?
How did you make decisions about which items, whether evidence and known samples or known samples and which approach was going to be used with those various items? How do you do that?
Well, for some of the items, we were requested to do a particular thing. Most of that would be PCR. For some of the items, umm, we were directed to do testing, and if possible, do RFLP testing. So for those items, we would have made an assessment of the quantity and quality of DNA that was extracted from those items, and then we would have proceeded to make some judgment as to whether we should try RFLP or go straight to PCR.
As far as the actual testing conducted in this case, do you have with you today the autorads from RFLP testing that was done?
Do you also have photographs from the various typing strips that were interpreted or results were obtained from after PCR amplification?
As far as the testing itself--and I'm referring to all of the testing conducted in your laboratory--did the controls work properly?
The controls worked properly for all of the testing with one exception, and we had a--very faint dots in one reagent blank for one of the PCR tests.
KEY QUOTEAll right. We'll return to that later. Was that, to your knowledge, the only instance in which that occurred?
Incidentally, why was--does the fact that you weren't informed of who these reference samples play any role in the testing itself?
In the course of testing--well, let me rephrase that, go back one step. As far as your not being informed of the identity of those known samples, is that unusual or normal?
It's unusual, but it's not the only time that we've received samples coded in some manner.
KEY QUOTEAs far as the results that were ultimately obtained, did they include indications to you of mixtures of DNA?
Well, in this circumstance, we're talking about the idea that the DNA that was extracted from the sample contains DNA from more than one person.
For an RFLP test--well, actually it's the same for both. Any time that you look at a single genetic location and you see more than two types for an RFLP test, that would be, instead of just seeing two bands, you saw three, or for a PCR test, would be instead of seeing just two types like an a and a B, you would see an A, a B and a C. Under those circumstances, you know immediately that you have DNA from more than one person.
If you view contamin--if you--let me back up a second. If you have--if those two DNA's are part of the original evidence as it was left at the scene, then in my view, that's not an instance of contamination. That's the true nature of the sample. If you want to back up and say are these sterile samples, no. We've got two DNA's that are mixed together, but that's not a good reference point for this kind of discussion.
With regard to the procedures--and you've had an opportunity to review all of the material relating to this case?
Have you had an opportunity to review all of the documents that you've described are kept in the course of testing in your laboratory?
From that review of the various documents and data, whether photographs or autorads themselves, do you have an opinion about whether or not correct procedures were used by the two analysts in this case, Julie Cooper and Paula Yates?
My opinion is that the procedures in the protocol were followed correctly in the testing in this case.
KEY QUOTEAs far as the procedures that were used in this case, in your opinion, are those proper scientific procedures for DNA typing?
Now, with regard to--and let's focus immediately on RFLP testing itself. Do you have with you an autoradiograph that depicts the three standards or known samples in this case?
And have you also-- well, first of all, do you have the original autoradiographs with you?
We don't release them until we come to Court. If they are left as part of the Court record, that's okay. But prior to that, we maintain the original data, which is the autoradiographs, in our custody.
For what reason? Actually, let me rephrase that question. In terms of the originals themselves, do they represent the best data available?
All right. With regard to the autoradiograph I mentioned that deals or demonstrates the results obtained from DNA from the three identified samples, that is without name, but identified as known persons, does that autorad--has it already been marked in this case?
Showing you exhibit 246, can we use that autoradiograph to show what the DNA appears or what it appears like for the three known samples in this case?
Your Honor, at this time, I have or actually the laboratory has made a number of copies of this particular autoradiograph that shows the three standards, that is the three known individuals. It has one evidence lane with nothing showing. And it would be my request that these copies be distributed to the jury.
That's with item 56 removed? Never mind. All right. Mr. Clarke, do you have enough to go around?
I take it this is for demonstration purposes at this point because we're not doing any comparison yet, correct?
The controls worked properly for all of the testing with one exception, and we had a--very faint dots in one reagent blank for one of the PCR tests.
My opinion is that the procedures in the protocol were followed correctly in the testing in this case.
If you have--if those two DNA's are part of the original evidence as it was left at the scene, then in my view, that's not an instance of contamination. That's the true nature of the sample.
It's unusual, but it's not the only time that we've received samples coded in some manner.