Ladies and gentlemen, before Mr. Blasier continues, I want to apologize to Mr.'Blasier for referring to the examination as scintillating and having an effect on the jury.
Numbers are a very important part of the defense in this case, from the defense point of view. And so, the fact that the numbers tend to be dry sometimes, and may have an affect on some of you, jurors should not detract from the importance of the case and I should not have referred to Mr. Blasier's examination as scintillating. But that's the nature of the subject matter and I do apologize for that.
Now, if you get drowsy, please let me know. You know, he didn't want to spend all of his effort in this examination to have it wasted on you if you're not able to pay attention.
It's very important that you do pay attention. And if you find that you're drifting off, let me know. There's no reason why you should be embarrassed to let me know because it's important that you all pay attention. So raise you hand or do something. Okay.
Also, I have to be looking at you and everybody else in this courtroom is looking at you, so you know, if you -- if you feel you concentrate by closing your eyes or something like that, have some second thoughts about that because everybody's going to be thinking your drowsing off. All right.
Dr. Cotton, the tests that are done in forensic applications of DNA applications are very complicated, aren't they?
Thank me.
When you got evidence sent to you by LAPD what -- particularly the Bundy drops, it was in the form of swatches, correct?
None of those bindles that you got from the Bundy drops had Andrea Mazzola's initials on them?
Doctor, the dots we haven't talked yet about. We've looked at Autorads, but we haven't talked about -- right there for now. We haven't really talked about what a PCR test result looks like.
Isn't it correct that with PCR test, you don't get something that looks like an Autorad, you get something called a testing strip that has dots on it?
Excuse me. It was clearer when you first -- when you first put it on.
MR. P. BAKER: Somebody touched the button.
(BY MR. BLASIER) We'll zoom in so you can see it better. I just want to just, very briefly, go over how you look at results from a PCR, DQ Alpha test. These happen to be DQ Alpha strips, correct?
And the dots, of course, they have little numbers next to them which correspond to the alleles that you're looking for, correct?
And again, the allele, that's just all we're talking about, is a piece of DNA at a particular location on a chromosome, right?
And sometimes we might get the same one from mom the same one from dad, in which case our type would be 1.1, 1.1 correct?
So that the dots that would light up would be the ones that would correspond to the 1.1, correct?
So a 1.1 would light up this dot and this dot, and there's another column at the far right that says all but 1.3 and that lights up when you get any allele that's different from 1.3, correct?
This happens to be, if we back out a little bit so Dr. Cotton can look at this. This is a DOJDQ Alpha testing strip and it includes item number 29.
Stop.
Let's zoom in on the number, I mean, on the label here. Okay.
See that, Doctor, LAPD number 29?
And I'm going to slide this over a little bit.
We can see -- let's zoom in on the 4 right there. There is a faint dot at the 4, correct?
Somehow, before you made it bigger.
Let's back off a little bit. That's better.
That tells you there is a 4 allele in that sample, correct?
Now, you ruled out Mr. Gold -- ruled out Mr. Goldman from this sample because he is a 1.3 and there is no dot at the 1.3, correct?
That tells you that Mr. Goldman's DNA wouldn't be there, correct, as far as the test results?
Well, I'm saying exactly what you alluded to earlier. There's a specific level of detection. And if you don't see something, doesn't necessarily -- that just means you can't see it. So we didn't see it. And therefore, based on what we saw, we ruled out that he was there.
Are you saying, Doctor, that this test in some instances you have, can have DNA in there that won't show-up?
This is a very good test. I can't think of any test that you could do that doesn't have some limit to what you can detect. And this has a limit to what you can detect, like every other DNA test that I'm aware of.
(BY MR. BLASIER) You can have somebody else's DNA in here and not know it from this test, correct? Small amounts?
And would you also agree with me that from this test result on number 29, there is a contributor to this sample that is someone other than either of the victims or O.J. Simpson?
I wouldn't agree. I don't think -- I think that would be an over statement of the data. All that you can really say is that there is another person here and.
You can't say anything about who it is or isn't because the data that tells you that another person is there, is very faint. And it's in our test, it was below the control dot. So that tells you that it's not necessarily a reliable result.
What that means when it's below the control dot is there could be some other alleles there and you may or may not be seeing them. So all you can say is there's another person. There are two people in this -- in this DNA and --
Well, that's what I'm saying is, I don't think that that's an accurate interpretation. It's consistent with somebody being in there who has a four. And we may -- they may be a 4, 4 or they may be a 4 something else and we may not be seeing what that something else is. So to just say it's a second person or a another person with a 4, 4 would be an over statement of the results.
So -- well, let's just look at the dots that are there for a moment. Okay?
They're consistent with someone who's a 4, 4, right, being in that sample?
That's right. If that was -- if that's the scenario that there's a person with a 4, 4, then that can't be any of those people.
Now, would you agree that there is certainly a fair amount of subjectivity that goes into interpreting these kind of strips in testimony of whether there are dots there or not and how strong they are and how weak they are?
And isn't it true that one examiner might interpret that same data differently from the way you've interpreted it?
And that's not particularly good for a forensic test, is it?
Do you prefer to have tests where the data -- where the same data is interpreted the same way, wouldn't you?
You would always prefer to have your test results be consistently interpreted but there are certainly always, with RFLP and PCR, going to be some variation in interpretations.
Doctor, I asked you to locate the polymarker testing strip for the reference samples. Were you able to do that?
Let me borrow this. I'll give it back to you at the end.
Let me ask you--
Let's do it this way.
This is civil 1275.
Obviously, you have to look at reference samples so you can compare your evidence to the people, right?
And the reference samples that you use, supposedly come from the people you know -- you know they come from and presumably it's a pretty good DNA, right?
And you wouldn't expect to see evidence of more than one person in a reference sample, would you?
Isn't it true, that when you were -- you ran Nicole Brown Simpson's reference sample, this is supposedly blood from her autopsy, in the GC system you found evidence of a B allele? The B lit up, didn't it?
I'm looking puzzled 'cause I don't -- I don't understand why you're pointing to the chart. It doesn't --
Actually, I'm only pointing to this.
As far as you're concerned, you found a faint B in her reference sample, did you not?
I don't think anybody else's DNA is in her reference sample. I think that faint B is there because there's a fair amount of DNA in that sample and that is a typical -- The correct term is cross-hybridization. That's a typical thing that can be seen. When you have a fair amount of DNA in a reference sample, you might have another dot lighting up just faintly.
KEY QUOTEAre you saying, Doctor, in that test sometimes you have a dot light up and it isn't DNA, right?
You're talking about a dot lighting up that is DNA or type of DNA that shouldn't be there, correct?
What I'm saying is that the fact that there is this faint B, would you -- would you be incorrect to immediately jump to the assumption that there is any contamination in that sample because there are much more common technical problems that can cause that faint B that have nothing to do with contamination of a sample.
All right.
So the dot that can show-up, that, you don't attribute to a person's type, correct?
And for any sample, you get 1.3's a lot, don't you that you say this isn't really a real dot we're just going to --
No. We don't do that. We write down exactly what we see on our records. We write down in our records, there's a faint B here. Then you go through and interpreting that, and is that meaningful; and what do you know about the test; and have you seen this before and has -- Is this reproducible?
You see it in other reference samples where you have a GC type AC and you do. And so you could -- there are two causes. One is it's a -- it's an artifact of cross-hybridization and it's typically seen. And the other explanation is what you were proposing; that is contamination.
Those two explanations have to be considered and there is no way to definitely tell one from the other.
That's not too bad a definition. I don't think I can come up with a better one right this second.
So that dot can be explained one of two ways. Either it's contamination or it's a dot that appears real, but isn't?
It's real. It's there and there's a real reason why that can happen. And it's a common reason why that can happen. So the dot's real. The color's real.
It isn't -- it's part of the fact that you're asking, you're doing a DNA test and every DNA test does not necessarily give you an absolutely tidy clean result every single time.
And your figures that you come up with in frequencies don't take that into account either, do they, Doctor?
I think I've agreed with you, many times, the frequencies only tell you how common or rare this group of traits is.
Now I want to ask you about fingernail scrapings.
You did some DNA tests on Nicole Brown Simpson fingernail scrapings, correct?
Now, fingernail scrapings, when you scrape something from under a person's fingernails you're going to get more than just blood if there's blood there. You're going to get skin tissue. You can get dead cells. You can get all sorts of things, sort of biological material, correct?
And your RFLP test or whatever test you run on an DNA test, doesn't distinguish whether it's blood that you're looking at or tissue, does it?
So isn't it true, that you would always expect, when you take scrapings under a finger -- person's fingernails and did a DNA test on it, you would expect to see their, find their DNA under there?
Now, if you found evidence of blood that -- let me rephrase that.
Red blood cells are tested for a genetic marker known as EAP, correct.
And if you had evidence of blood under those fingernails with an EAP type, different from Nicole Brown Simpson, that would indicate blood under there from a different person?
Okay. The fact that her DNA is there from blood tissue, whatever, is not unusual in and of itself, correct?
And did you come up with an estimate of the quantity on that? It had over a thousand, didn't it -- thousand nanograms?
I know that we did an estimate. I haven't looked at that, so I don't know how much it had. Well, besides, I don't know if we got everything that there was.
Well, I don't want you to take time to do that. Do you remember any stain that had more DNA than that one?
I can't answer it, may have had the same amount as in the Rockingham blood drop. I mean, I can't answer that without going into my notes and doing the calculation and then telling you.
Now, the Autorad we looked at had one lane for Nicole Brown Simpson and one lane for the sock, correct?
(BY MR. BLASIER) When you were talking about Ms. Brown Simpson's blood before, you said that you wouldn't always necessarily expect to have a completely clean sample, right?
Well, the lane that's on there is from her reference sample which is the same reference sample that we already talked about, correct?
And the lane that's on there for the sock, that can be -- you have no way of knowing the source of the blood on -- or how that blood got on that sock, do you?
Okay.
And blood can be taken from a reference file and put on a piece of cloth and wiped on a sock and you can get a test result, correct?
KEY QUOTEObjection. Assumes facts not in evidence. Misstates the evidence. Improper hypothetical.
So are you asking me, could someone take some blood and wipe it on a sock and then you would get a type?
Or you could take some blood and wipe it on a cotton swatch and then wipe it on a sock, couldn't you?
You can't tell from the intensity of the lanes on that Autorad where that blood came from, can you?
Whether it came from a reference tube or a wound, can you?
No, I do think you can make some conclusions about whether it came from the reference tube, from the patterns, from the degradation in the two patterns in that film.
Now, I want to talk about the formula that you used to get these big numbers called the product rule, correct?
And again, the estimates of frequencies from populations of how frequently you might see a particular banding pattern from a particular population, correct?
Now, you don't actually go out like for your 1 and 530 billion there aren't 530 billion people in the world.
By the way, the number that you give is not a number, that's the probability of guilt; is it?
It's not even the probability that someone other than Mr. Simpson is the source of the stain; is it?
No. It's just simply how often you would expect to find this particular group of genetic characteristics.
Isn't it correctly stated that as the chance if you went out and picked somebody in the world at random, the chance that they would have the same pattern?
Now, since you can't measure everybody in the world, you have to take a sample of people, correct?
Now, there's an issue, when you're talking about comparing a band from one part of the DNA, one allele to another allele from the same person's DNA as to whether there's any relationship between the two, correct?
Do you know what I'm getting at?
Okay. Let me use analogy.
If you were concerned about trying to figure out how many people in the Norwegian population had both blond hair and blue eyes, you could go and count the number of people that have blue eyes and find out what percentage that is, find out what percentage the people with blond hair is. But it would be inappropriate to multiply those two numbers together, wouldn't it?
And the rule that you use, it's called the product rule, and all of these calculations assumes that there is no relationship between those two fragments in a given person's DNA, correct?
Right. It means that if you have type A, that you're not anymore or less likely to have as your second type an A or a B or a C, for that matter or whatever.
And there's been a substantial controversy among scientists in the last five or six years about whether that's true or not with these kinds of testings, haven't there?
There's been a lot of discussion about it but I think that controversy, as you phrase it, is pretty much settled.
Doctor. You've been testifying in the last five years about this controversy, have you not?
That's primarily when you testify. It's in hearings about that controversy; isn't it?
I testified many times about this, but that's not the primary focus of most of the testimony. But yes, of course, I've testified a number of times.
The field of discipline that we're talking about here are molecular biology, population genetics and statistics, right, theories, the kind of three areas that you borrow expertise from to do these calculations?
And to -- so in order to use this product rule, when you're talking about multiplying frequencies together, it doesn't work if there's a relationship between one band on a person and another band?
Now, there's another thing going on here as well, is there not?
That is, that you can only sample a certain number of people by which to get frequencies from. For instance, if you counted up in a group of Norwegian people, how many people had blond hair and blue eyes, let say you got a figure of 50 percent, it would not be appropriate to say therefore, 50 percent of the Caucasian population all over the world is going to be half blond hair, blue eyed, correct?
No. That might be a good figure for Norway, but it wouldn't necessarily be a good figure for everywhere else.
That's because groups of people in different locations, in different ethnics sorts, have different characteristics, don't they?
And one of the major issues that has been the subject of testimony in scientific discussion in this field is whether or not the groups that you use to come up with these large numbers are really representative of the whole group of people, correct?
That's one thing. That's part of that issue and the issue is more specifically by the groups that you have representative of other groups. For our purposes, would be -- are they representative of other groups in the United States. We don't need to worry about the whole world, but we do want to worry about, are they're representative of people in the United States.
Okay. Doctor, now for item number 12, where you gave us a number 1 and 1.2 billion, by the way, is that the African American data base or do you know?
Not sure if that's correct, but it's very few, so could be two, could be ten, but nonetheless, all that qualifies as not very many.
That's the underlying data from which you get a number from 1 in 170 million, correct?
KEY QUOTEAnd that doesn't match Mr. Goldman, Ms. Brown Simpson or O.J. Simpson, does it?
I don't think anybody else's DNA is in her reference sample. I think that faint B is there because there's a fair amount of DNA in that sample and that is a typical -- The correct term is cross-hybridization.
That's the underlying data from which you get a number from 1 in 170 million, correct?
It's very clean.
Blood can be taken from a reference file and put on a piece of cloth and wiped on a sock and you can get a test result, correct?