Mr. Sims, Mr. Blasier was asking you some questions before about cross-hybridization and your reading of some of these DQ alpha strips.
I'd like you to explain to the jury this cross-hybridization phenomenon.
Yes.
The cross-hybridization phenomenon can occur because some of those alleles are very similar in sequence and the differences are very slight among the probes that we're looking at.
So, for example, sometimes you will have samples that are similar in their sequence because the sequence that's on the probe that's, say for example, the 1.3 probe, so that you can get a little bit of a back -- what we call a background or cross-hybridization result.
And by sequence, Dr. Cotton had explained during her testimony that one of the ways that we can distinguish between people's DNA is by the sequence of the base pairs.
And are you saying that the sequence of the base pairs in these 1.1, 1.2, 1.3 alleles is not that far apart?
Well, that's correct.
And so what you can see is that this is not always an all-or-none phenomenon. I mean, anything that happens in chemistry, we will generally have a little bit going one way, or all we have is some of it going one way.
But I'll also have some going such that you could see cross-hybridization. That's why it's a weak reaction.
(BY MR. LAMBERT) And as part of the system at the Department of Justice, when somebody makes a call on one of the DQ alpha strips, like was done on item 31 here on the Bronco, how many people look at that DQ alpha strip before it goes out into the Department of Justice report?
There would be three individuals. The first person who does the -- actually typing analysis; then we have a second reader look at them; and then a supervisor then reviews them before they're reported.
I'm going to object. This misstates the testimony. He didn't -- he said -- he didn't say very weak.
That misstates his testimony. He didn't concur with the way it's characterized on the chart.
By the way, when that item 31 was read, who else was present besides the Department of Justice personnel?
Now, Mr. Blasier also showed you the reference chart that he has, showing the testing of the reference samples?
And trying to imply in his questions that there was some contamination in those reference samples; do you remember that?
We'll have to get the Court number for this. I'm not sure what it is right now.
I'm actually using Mr. Sims' copy of this, but there is --
What we're looking at is a photograph of the typing strips. And this is just a portion of those strips.
You'll recall those; there were nine dots all along that. So it's a -- we're looking at a couple of the dots.
This is Mr. Goldman's reference blood sample extract that's being tested for DQ alpha type. 1.3 allele is present. We can't see it over here, but it also has a 4 allele; and those two combined to light up this dot also.
As you'll recall, in the cross-examination we talked about there being some faint activity in the 1.1 region of that dot, and I wanted to show just what -- how faint this is, what we're talking about.
In other words, the point is, I'll let you draw your own conclusion, certainly, but it's extremely faint.
Yes.
There is the strip for Nicole Brown. Her type is a 1.1, 1.1. What we were talking about is being maybe very faint in the background, was in this 1.2 region and the 1.3 region. And if I really strained my eyes, I might be able to see something in those regions, but it's just -- it's extremely faint.
There's another point of this. This is what we're talking about. There's no doubt to me about what these particular types are. And sometimes you do see this weak background, and that's just to show you how weak the background really is.
And in your professional judgment, Mr. Sims, was there any contamination in the reference samples?
No. I think that's a pretty far-fetched idea, particularly when one remembers that these reference samples contain very large amounts of DNA.
And so that if you were to take any kind of traces of contaminating DNA, those contaminating traces would have to be extremely large to even show up in a reference sample, because now we're talking about a sample from this, the victims' reference samples that have a lot of DNA associated with them, micrograms.
And so that any contamination to show up, even at a trace level, would have to be extremely -- would have to be extremely substantial.
KEY QUOTENow, let me turn to another subject.
Mr. Blasier talked to you a lot about the amount of nanograms in various evidence items.
Is it, in your experience, routine to have varying amounts of DNA in the evidence samples that you receive?
Well, it goes to how much was collected, how uniform the sample is across a swatch, the kind of micro environment the stain is in, how long this stain's been out there. All those things are factors that could affect that. And so we typically see a tremendous amount of variation.
And the Department of Justice Laboratory, did it also get all of the swatches for any particular evidence item, or did it just get some portion of it?
I think it was both. In some cases, we got portions. In other cases, I believe we got almost all, but I'm not sure of that.
For example, item number 52, where Mr. Blasier was comparing the amount of nanograms in 52 to 117, which is the back gate, Cellmark actually got swatches for item 52, as well?
Yes. They -- for example, on that item, they certainly got the lion's share of those. We got little bits of cuttings, two little bits of cuttings.
When you were sharing, I think you said something like 3.5 nanograms that you got in your item 52, that doesn't take into account the 200 nanograms that Dr. Cotton talked about that she saw in item 52; is that right?
Okay.
Now, let's talk a little bit more about this concept of identifying bands in the RFLP test.
That RFLP procedure with that type of approach has been done, now, for -- going on ten years.
And is the technique that you're -- that you have described, a commonly accepted technique in the scientific community?
In fact, haven't there been some national committees that have discussed that very technique?
And when you do this, these band matches to declare a match between an evidence item and a possible person, do you rely on just one probe match, or do you always require more than that?
So when you get a nine-probe match like you did on the socks, matching to Mr. Simpson, with the frequency of 1 in 57 billion to 1 in 150 billion, what level of confidence do you have in that match?
KEY QUOTEI have a great deal of confidence because if it weren't from that particular individual, or there was really not a true match, you would see some shifting at some point that they were clearly different.
They were not.
KEY QUOTENow, one final point.
Mr. Blasier asked you some questions about the tests that you did on the socks.
And I'll put this up, just to remind everyone what you're talking about.
First I've got to turn this on. (indicating to Elmo).
Let's see if you can -- if we can focus this.
This is my first time.
(BY MR. LAMBERT) Okay.
Now, you tested -- compared in your tests here, some portion of the sock evidence to get these bands to some of Nicole Brown's blood; isn't that right? Blood from Nicole Brown?
Now, the comparison that you made, what was the source of the Nicole Brown reference blood that you used?
Those samples, it was my understanding, were the ones that were made by the coroner's office. In other words, the stain was made by the coroner's office because there was some indication that the other reference samples, that the other stains that had been made, had some problems with degradation.
So, in other words, what Dr. Cotton testified about, which was the reference vial taken by the coroner that was degraded, that's not what you --
Objection. Misstates the testimony. Dr. Cotton never said she tested the reference vial.
(BY MR. LAMBERT) Dr. Cotton testified that the blood she tested, which was taken from the reference vial, was degraded. That isn't that same source of blood, is it?
So can you explain for us, to make that point clear, what -- how the coroner's office sometimes takes a swatch and a reference vial?
Are you familiar with that procedure?
Well, I'm familiar with some of the operations of the coroner's office, having worked there at one time; but also, more presently, my familiarity is with how they prepare samples from homicide victims, for example, and they make blood stains on cloth.
And that's what I was informed was the situation here, was that there were these blood stains that the coroner's office had made on the cloth, and we tested those because the ones that were on the Fitzo cards showed some degradation.
The reason that you asked for the blood stains on the cloth is because the Fitzco cards taken from the reference vials showed degradation?
Well, I -- that's correct, except I don't think we asked for it; I think there was some information from the District Attorney's office, on talking to Cellmark, that there was this problem.
I think that's a pretty far-fetched idea, particularly when one remembers that these reference samples contain very large amounts of DNA.
I have a great deal of confidence because if it weren't from that particular individual, or there was really not a true match, you would see some shifting at some point that they were clearly different. They were not.
So when you get a nine-probe match like you did on the socks, matching to Mr. Simpson, with the frequency of 1 in 57 billion to 1 in 150 billion, what level of confidence do you have in that match?
Dr. Blake. Dr. Blake, representing Mr. Simpson? Yes.