Cross-examination of Dr. Robin Cotton (part 1)

📄 Cross-examination of Dr. Robin Cotton (part 1) — Thursday, November 14, 1996

Address:

C:\DEPT103\CIVIL\1996\NOV\14\CROSS-EXAMINATION-OF-DR-ROBIN-.DOC

TRIAL

▲ Day 15 of 57

◀ Exhibit receipt Sidebar: RFLP match meaning ▶

Witness: Dr. Robin Cotton
Examiner: Robert Blasier
Called by: Plaintiff • Date: Thursday, November 14, 1996 • Utterances: 284

Defense attorney Robert Blasier cross-examines Cellmark DNA expert Dr. Robin Cotton in the civil trial, first establishing her compensation for working with the plaintiffs after taxpayers funded her criminal trial work, then methodically walking through DNA structure and RFLP testing limitations. The core of the examination builds toward a technical concession: that RFLP match windows are wide enough that 999 out of 1,000 fragments within the window could theoretically come from different people, and that five probes are insufficient to establish unique identity.

# 1 Q:

Dr. Cotton, can you give us an estimate of the amount of time that you spent on this case when you were working for the prosecution, just approximately?

# 2 A:

The number of hours I put in?

# 3 Q:

Yes.

# 4 A:

I don't know. A lot.

# 5 Q:

A lot. Didn't you?

# 6 A:

Yes.

# 7 Q:

And the tests that were done on the 23 items were paid for by tax payers of Los Angeles County, correct?

# 8 A:

Yes, they were.

# 9 Q:

And all of your time that you spent in the criminal case were paid for by the taxpayers of Los Angeles County?

# 10 A:

That's correct.

# 11 Q:

Now, it's -- have the plaintiffs reimburseed taxpayers of Los Angeles County for any of that work.

# 12 MR. LAMBERT:

Objection. Irrelevant.

# 13 THE COURT:

Sustained.

# 14 Q:

(BY MR. BLASIER) How many hours have you spent working for the plaintiffs in this case?

# 15 A:

Probably, including the time that I've been here?

# 16 Q:

Yes.

# 17 A:

Probably about eight or nine days.

# 18 Q:

And what do you charge per day?

# 19 A:

For my time here, the company will charge $1200 a day for time that I spend in the office. Some of that time is in short chunks and doesn't really get charged at all and if it's a substantial block of time, it would be $200 an hour.

# 20 Q:

You have no personal knowledge as to how the evidence was collected, preserved and packaged before it was sent to your lab?

# 21 A:

That's right.

# 22 Q:

Would you agree with your -- that your test results are only as good as the evidence that you're given by an outside agency?

# 23 A:

Of course,

# 24 Q:

And if you're given evidence from an outside agency that has been contaminateed or degraded or tampered with or whatever, you can't make it any better, can you?

KEY QUOTE

# 25 A:

No.

# 26 Q:

So your test results are only as reliable as the evidence that you get?

# 27 A:

Yes.

# 28 MR. BLASIER:

Your Honor, I need to get some exhibits back here.

# 29 ( Pause in the proceedings.)

# 30 (Chart entitled "Where is DNA Found" displayed.)

# 31 MR. BLASIER:

I think that's exhibit 273.

# 32 Q:

(BY R. BLASIER) Doctor, can you see that from where you're sitting?

# 33 A:

Sure.

# 34 Q:

Now, I want to ask you a couple more questions about what DNA is to try and give us a conceptual framework of what we're talking about. Every cell that has a nucleus has DNA in it, correct?

# 35 A:

Yes. We have about six trillion cells in our body, correct?

# 36 A:

I don't know.

# 37 Q:

That's an estimate that's given.

# 38 A:

If it's in some text book somewhere, I would certainly accept that.

# 39 Q:

That's 6 million, million, right?

# 40 A:

Yes.

# 41 Q:

And most of those are nonred blood cells, correct?

# 42 A:

Yes.

# 43 Q:

Now every one of those cells has the same DNA in it as every other cell?

# 44 A:

Yes.

# 45 Q:

So if you take some DNA from hair, it's going to be the same as DNA from your blood from your skin, from other bodily tissue, correct?

# 46 A:

Yes.

# 47 Q:

And that's one of the ways you can compare hair sample with blood sample with DNA technology, correct?

# 48 A:

Sure.

# 49 Q:

Now, going back down to the lower level here, the structure of DNA, you described it as a ladder type structure?

# 50 A:

Yes, I did.

# 51 Q:

It's like a coiled up ladder, correct?

# 52 A:

Yes.

# 53 Q:

And it's made up of only four molecules, correct, that are of significance to us.

# 54 A:

Yes.

# 55 Q:

That's the A, C and the G and T?

# 56 A:

Yes.

# 57 Q:

Now, in a single cell the DNA in one cell is you have 6 billion of these base pairs or 6 billion rungs of the ladder in every cell, correct?

# 58 A:

Exactly.

# 59 Q:

And 3 billion of the cells, ru --- rungs you get from mom and 3 billion you get from dad.

# 60 A:

Yes.

# 61 Q:

We can think of it in terms of a tinker toy ladder that has two hubs and a stick in the middle through the rung. And the left hub is going to be an A and the right hub is going to be a T. The right hub could be a C and the left hub could be a G?

# 62 A:

Yes.

# 63 Q:

You can figure out how these go together, round letters go together. A and C and G -- I'm sorry, guess you can't do that. Anyway, they only go together one way, correct?

# 64 A:

Yes.

# 65 Q:

Okay. Now, 3 billion base pairs, if we want to try and understand the scale of this, if you think about a little toy ladder, like a kid might have on a fire engine, if the rungs of that ladder are half an inch apart, the entire DNA, if it was stretched, end to end, would be 3 billion half inches, correct?

# 66 A:

Yes.

# 67 Q:

I didn't do the math. It turned out to be about 25 thousand miles. Does that sound right?

# 68 A:

I haven't done the math.

# 69 Q:

You can assume that hypothetically.

# 70 A:

Fine.

# 71 Q:

Once around the world.

And the second 3 billion pairs of rungs, that comes from the other parents, is the same length, correct?

# 72 A:

Yeah. Yeah, about.

# 73 Q:

Okay.

So you can think of this as two ladders that are side by side that go around the world?

# 74 A:

Well, only if the base pairs are half an inch apart.

# 75 Q:

Right?

# 76 A:

Which they're not.

# 77 Q:

You can't see it without a microscope?

# 78 A:

Yes.

# 79 Q:

And you can't even see the individual molecules without extremely sophisticated equipment?

# 80 A:

That's right.

# 81 Q:

Now, when you do an RFLP test, would you say, is the -- let me ask you this:

Isn't it true that if you have the DNA from a piece of evidence and the DNA from a suspect, if there is a single rung of that ladder that is different from one to the other, it came from different people?

# 82 A:

Yes. If you have two RFLP patterns and you have a band in one that is different than --

# 83 Q:

That wasn't my question, Doctor. A single base pair difference --

# 84 A:

Oh.

# 85 Q:

-- Between evidence and suspect means they didn't come from the same person, correct?

# 86 A:

Well, that theoretically is correct, but you --

# 87 Q:

Thank you.

And when you do an RFLP test, what is the average fragment lengths that you look at?

# 88 A:

Your -- the range of fragment length that are looked at on our gels are 1600 to about 23,000 base pairs.

# 89 Q:

Okay. So from 1600, which is about 800 inches, under my scenario, to 23,000 half inches or about 12,000 inches, correct?

That's all you look at?

# 90 A:

Yes.

# 91 Q:

Out of the whole 25,000 mile ladder, correct?

# 92 A:

Yes, we're just looking at a small section of DNA.

# 93 Q:

An extremely small section of DNA?

# 94 A:

Yes, compared to the total, sure.

# 95 Q:

And the polymarker system that -- the alleles that you look at in the polymarker system are even smaller, aren't they?

They're in the neighborhood of 250 base pairs, correct?

# 96 A:

Yes.

# 97 Q:

Or 120 inches, like ten feet compared to the whole chain?

# 98 A:

If we --

# 99 Q:

Isn't that correct?

# 100 A:

I don't know about your numbers. If we just stick with base pairs, then I'll be able to answer your questions a little bit better.

# 101 Q:

250 out of 6 billion, correct or 3 billion?

# 102 A:

For each locus you're looking at a small piece, which may be about 250 base pairs.

# 103 Q:

You're not looking at any of the rest of the 6 billion base pairs, are you?

# 104 A:

No.

# 105 Q:

Now, you actually don't have one continuous piece of DNA that goes all the way around the world. It's broken down into 23 sections?

# 106 A:

It's broken down into 46 sections.

# 107 Q:

For each ladder is 23, one from mom one from dad, correct?

# 108 A:

Right.

# 109 Q:

That corresponds to the chromosomes?

# 110 A:

Yes.

# 111 Q:

So it's, you know, one twenty-third, approximately, of the ladder is going to be one chromosome and scientists have given these numbers, chromosome number 1, number 2, et cetera?

# 112 A:

Yes.

# 113 Q:

And if you go down below, within a chromosome, they're broken down into the smaller segment or they're blocked out in smaller segments that are called genes, correct?

# 114 A:

They can be, yes.

# 115 Q:

Okay. And a gene is simply a series of base pairs that could have a wide variations in length, but it's just by definition, scientists have defined certain things to be a gene?

# 116 A:

A gene is a functional unit that actually conveys information to the cell, yes.

# 117 Q:

So a particular section of the ladder that might have 100,000, 200,000 base pairs scientists might say, we think that this is connected to hair color, for instance, and so that's a gene that might be conected to hair color?

# 118 A:

Yes.

# 119 Q:

An allele is a fairly short segment of DNA, that's all it is, correct?

# 120 A:

An allele could be very long. It could be very short. It doesn't -- there's no connection between an allele and length.

# 121 Q:

But the alleles you look at don't go any higher than 23,000 base pairs?

# 122 A:

Well that's correct for this test. But you could have an allele of a gene that was 100,000 base pairs.

# 123 Q:

For purposes of this test, you're only looking, at the most, 23,000 base pairs?

# 124 A:

For one, for one locus.

# 125 Q:

Okay. If the roughly 10,000 base pairs average from 1600 to 23, -- 20,000 -- excuse me -- and in it's 5 probe matches that you were talking about, there are two bands for each probe, correct?

# 126 A:

That's right.

# 127 Q:

And again, we're talking about two side by side segments of the ladder; one from mom, one from dad in each probe?

# 128 A:

Yes.

# 129 Q:

And those five segments total together, if our average is 10,000 base pairs per segment, is only 50,000 base pairs that you're looking at for an RFLP test?

# 130 A:

For five.

# 131 Q:

For five probes?

# 132 A:

Yes.

# 133 Q:

And this is the one that you say conveys the most information of all -- of all the tests?

# 134 A:

Yes. Of the testing that people -- labs are doing today, this is the most powerful test.

# 135 MR. BLASIER:

Now, can we get the diagram board, Phil?

MR. P. BAKER: Yes.

# 136 Q:

(BY MR. BLASIER) Doctor, what is a nanogram?

# 137 A:

It's one times ten to the minus ninth grams.

# 138 Q:

It's a billionth of a gram, correct?

# 139 A:

Yes.

# 140 Q:

And how many grams are in a pound, 454?

# 141 A:

I believe so, yes.

# 142 Q:

So a nanogram is an extremely small amount; is it not?

# 143 A:

Yes.

# 144 Q:

How many nanograms are there estimated to be in a single drop of blood?

# 145 A:

I'm not sure how to -- The way to answer that question is to think of a drop in a more precise volume. We get about 10,000 nanograms from an amount of blood that would be a little less than the size of this pen top.

# 146 Q:

This is exhibit 987.

# 147 (The instrument herein referred to as chart entitled "Small Amounts of DNA From Specs of Blood" was marked for identification as Defendants' Exhibit No. 987.)

# 148 Q:

You heard the figure that there are 1,000 to 2,000 nanograms per -- I'm sorry. Give me that again, your figure of how many nanograms in a -- in a size of blood the size of --

# 149 A:

We get about 10 micrograms, which is about 10,000 nanograms in about 700 microliters of blood.

# 150 Q:

Okay.

# 151 A:

So you could calculate, sort of. You could go down and workout how many -- what volume of blood would produce a certain amount of nanograms and I haven't done that recently.

# 152 Q:

Okay. Just to get a rough estimate, 20 nanograms of blood is going to be extremely small; is it not?

# 153 A:

Yeah. It's going to be small but I can't tell you how small.

# 154 Q:

Okay. And two nanograms is going to be, of course, one tenth as small as 20; isn't it?

# 155 A:

Yes, of course.

# 156 Q:

How many drops of blood are there in a CC, cubic centimeter?

# 157 A:

I don't know. I mean, how big a drop is, is a very subjective thing. So in the laboratory, you don't measure things in terms of drops. So I don't really have a figure for you -- for that. I don't know.

# 158 Q:

Have you heard the figure 20? Is that an approximation?

# 159 A:

I haven't heard any physician -- I don't know a common figure for a drop. I'm not aware that there's a common figure for a drop.

# 160 Q:

Have you heard an estimate of 20 drops per --

# 161 MR. LAMBERT:

Objection. Calls for hearsay. Irrelevant.

# 162 DR. ROBIN COTTON:

There may be such an estimate. I'm just not aware of it, you know. That's just the state of what I know.

# 163 Q:

Let's -- can we put the pad up for a second?

# 164 (Counsel displays drawing pad.)

# 165 Q:

Can I borrow your black pen there?

# 166 A:

Sure.

# 167 Q:

I'm going to try and draw this.

Now there are a number of different terms that are used in forensic science for when two things appear to be -- or could come from the same source, aren't there?

# 168 A:

Yes, sure.

# 169 Q:

And I've used the term "match" in the context of DNA testing, correct?

# 170 A:

Yes.

# 171 Q:

And none of the tests that you do are capable of establishing or do establish unique identity, do they?

# 172 A:

No, I don't agree agree with you.

# 173 Q:

Well, the estimate that you come up in terms of numbers are statistical estimate based on some formulas that you do, correct?

# 174 A:

Yes.

# 175 Q:

And you cannot possibly look at all of the DNA in a sample. You're only looking at a very small part of it, correct?

# 176 A:

That's correct.

# 177 Q:

And these tests do not establish a unique identification the way I've used them, do they?

# 178 A:

If you do, if you have available to you, a series of a large enough series of problems on an RFLP test. I'm not saying that five is necessarily large enough. I'm just saying if you have enough, I would say perhaps ten or more, I don't think there's a scientist who would argue with you that you've established identity.

# 179 Q:

But no scientist will tell you that with five probes you've established a unique identification, will they?

# 180 A:

I don't think that. Yes, I agree that five probes would not be necessarily considered to be an identification.

# 181 Q:

And you've heard the term "match" used in the context of, for instance, hair and fiber evidence where it means a hair could have come from the suspect or, then again, it might not have, right?

# 182 A:

Yes.

# 183 MR. LAMBERT:

Objection. Beyond the scope. Irrelevant.

# 184 THE COURT:

Excuse me. There's an objection. Objection sustained as being beyond the scope.

# 185 MR. BLASIER:

Okay.

# 186 MR. LAMBERT:

Like the answer to be stricken.

# 187 THE COURT:

Stricken.

# 188 Q:

(BY MR. BLASIER) I'm trying to name what a match is for purposes of the jury's understanding this. Okay, Doctor?

# 189 A:

Okay.

# 190 Q:

Now, with RFLP technology, which provides the most information, you look at bands on an X-ray, correct?

# 191 A:

It's not an X-ray, but you look at bands on a -- on the spray film.

# 192 Q:

Okay. But -- and if we consider one band to be from the evidence and one band to be from the suspect -- you with me so far?

# 193 A:

Um-hum.

# 194 Q:

And with RFLP, you look at an average of 10,000 base pairs per band, an easy round number, okay?

So let's say that you have determined that the evidence band is 10,000 base pairs?

# 195 A:

Yes.

# 196 Q:

In order for your suspect to match the evidence, the suspect's corresponding band has to be 10,000 base pairs correct?

# 197 A:

No.

# 198 Q:

Well, let me rephrase it.

In order for the DNA from the suspect to be identical to the DNA from the evidence, it has have the same sequence and the same number of base pairs?

# 199 A:

Yes.

# 200 Q:

Okay. So for identity to be established, would this one section, anyway, you've got to have 10,000 base pairs from the suspect that matches exactly the 10,000 from the evidence, correct?

# 201 A:

Right. But --

# 202 Q:

Okay.

# 203 A:

Let -- that wouldn't establish identity.

# 204 Q:

Correct. Well, okay.

Even that's not enough to establish identity?

# 205 A:

Of course not.

# 206 Q:

The sequence itself could be different?

# 207 A:

Even if the sequence was identical, you'd still not have established identity.

# 208 Q:

You have a lot of other DNA that you're not even looking at, you're only looking at one small piece?

# 209 A:

Yes.

# 210 Q:

This is what you look at with one band of one probe?

# 211 A:

Yes.

# 212 Q:

Correct.

Now, if it turned out that your suspect band was 9,999 and your evidence band is 10,000, those two samples came from different people, correct?

# 213 A:

In theory, that would be correct.

# 214 Q:

In truth that's correct; isn't it?

# 215 A:

In practice, we can't make that determination.

# 216 Q:

Doctor, In theory that's true; isn't it?

# 217 A:

Yes. But you didn't --

# 218 Q:

Thank you.

# 219 A:

You --

# 220 Q:

We'll do this step by step. Okay?

Now, for 10,000 base pair segments, what is the window size that you use -- explain that in a minute. Explain to me what the window size is approximately in percentages?

# 221 A:

I think it's around probably 2.6 percent.

# 222 Q:

Plus or minus 2.6?

# 223 A:

Yeah. I don't have those figures with me but that will have to do as a --

# 224 Q:

Okay Let's take plus or minus 2.5, little easier number to work with.

# 225 A:

Okay.

# 226 Q:

Now, if you have a suspect sample, that is, percentages are 9,500 base pairs long and your evidence sample is 10,000, you know that these came from two different people if you know those numbers precisely?

# 227 A:

If you knew the numbers precisely, you would know that.

# 228 Q:

Okay. And further you would know that if the suspect's base -- Fragment was 10,500 base pairs long you would know, if you were able to determine those numbers precisely, that these two samples came from different people, correct?

# 229 A:

Yes.

# 230 Q:

And virtually all there are a thousand possibilities between 10,500 and 9,500 of base pair lengths, correct?

# 231 A:

Yes.

# 232 Q:

Only one of those, 1000 possibilities is going to be identical to your evidence, correct?

# 233 A:

Yes.

# 234 Q:

999 of them are going to be a different person, correct, if we're able to measure this?

# 235 A:

If you're able to measure it, that would be correct.

# 236 Q:

Now, you're not able to measure it this way are you?

# 237 A:

No.

# 238 Q:

And because the measurement techniques that are used are not sophisticated enough to measure fragment length you give yourself a window within which to call something a match, don't you?

# 239 A:

Yes all RFLP labs do that.

# 240 Q:

What you say is gee, since we can't measure this very precisely we're going to say if it's 10,500 base pairs, we're going to call it a match to 10,000, aren't you 'cause that's within your window; isn't it?

# 241 A:

Well, forgetting the math for a minute, if it's within the window, then it's called a match. And if it's not within the window, then it would either be an inconclusive or an exclusion.

# 242 Q:

Okay. So every one of the thousand possibilities in here within this range, you will call a match. But only one of them out of the thousand is truly a match, correct?

KEY QUOTE

# 243 A:

Theoretically, if you were -- theoretically, yes, what you're saying is absolutely true.

KEY QUOTE

# 244 Q:

Okay. Thank you, Doctor?

# 245 A:

But we don't have that information.

# 246 Q:

You're not -- you can't measure it good enough, can you?

# 247 A:

It's not a measure -- matter of measuring it good enough, it's what is the technique able to do.

# 248 Q:

The technique is unable to measure it with any, or more precision than this, correct, Doctor?

# 249 A:

Yes. That's correct.

# 250 Q:

And the wider this window is, the more -- the greater the chance is that you're going to call somebody a match, a suspect and an evidence band as a match, when it came from different people, correct?

# 251 A:

I don't think that follows, no.

# 252 Q:

Oh, you don't. Okay. And this is true, this window that you use, because of measurement, is used for every one of the problems that you use in RFLP, correct?

# 253 A:

There is a window, a size window, yes, that you compare for each probe, for each band.

# 254 Q:

So for a five probe match, where you're looking at ten bands, you've got this, plus or minus, roughly five percent. I know it changes for the size of the band, but for the sake of discussing it, you've got this same window, if you will, on every single one of those bands, don't you?

# 255 A:

Yes, you do.

# 256 Q:

Could we have this marked next in order, please?

# 257 THE CLERK:

2184.

# 258 MR. BLASIER:

2184.

# 259 (The instrument herein referred to as a Hand Drawn Diagram by Mr. Blasier was marked for identification as Defendants' Exhibit No. 2184.)

# 260 Q:

(BY MR. BLASIER) The one you gave was 530 billion. I think it was a five probe match using this technique. Would you allow yourself a large -- or a window -- I won't say a large window, to call something a match when you can't tell that it's the same, can you?

# 261 A:

We use this technique to come to that number, yes.

# 262 Q:

And your computer program that you talked about, that doesn't make it any more accurately than this either, does it?

# 263 A:

Computer program, I talked about the computer imaging system; is that what you're referring to?

# 264 Q:

Yes.

# 265 A:

The computer imaging system is what you use to come up with the number in base pairs that the bands are.

# 266 Q:

Okay. And -- but that's not a precise number either; is it?

# 267 A:

No. Each one of those measurements is as good as the technology will allow.

# 268 Q:

Okay. Of your 1 in 530 billion sample that you told us about, which was -- which one was that?

# 269 Q:

Do you remember what that was?

# 270 A:

The sock.

# 271 Q:

It's a five probe match, 10 band, correct?

# 272 A:

Yes.

# 273 Q:

You have your sizing sheet with you?

# 274 A:

Yes, I do.

# 275 Q:

Can I take a look at that these, please?

# 276 A:

Which one do you want to look at?

# 277 Q:

All of them. You don't have them on one page? Do you have them on one page?

# 278 A:

All of the bands for?

# 279 Q:

For that match?

# 280 A:

No. The sock?

# 281 Q:

Correct, for that 1 in 530 billion that you gave us.

# 282 A:

Yeah. It will take me a few minutes to find it.

# 283 Q:

Okay. Your Honor this might be a good time to give her a chance to --

# 284 THE COURT:

Okay. Ten-minute recess, ladies and gentlemen.

Temperature

tense

Key Quotes (4)

Robin Cotton

If you're given evidence from an outside agency that has been contaminated or degraded or tampered with or whatever, you can't make it any better, can you? No.

Establishes that Cotton's results are entirely dependent on the integrity of LAPD's evidence collection and handling — the defense's central attack.

Robert Blasier

Every one of the thousand possibilities in here within this range, you will call a match. But only one of them out of the thousand is truly a match, correct?

The central argument of the cross: the RFLP matching window is so wide that the technique cannot distinguish between a true match and hundreds of near-matches from different people.

Robin Cotton

Theoretically, if you were -- theoretically, yes, what you're saying is absolutely true.

Cotton's reluctant concession to Blasier's window argument — a major methodological admission, even though she tries to qualify it with 'in theory.'

Robin Cotton

I don't think that five probes would be necessarily considered to be an identification.

Direct concession that the five-probe RFLP test used in this case does not establish unique identity.

Evidence (4)

Exhibit 273

Chart entitled 'Where is DNA Found'

displayed during DNA structure explanation

Defendants' Exhibit 987

Chart entitled 'Small Amounts of DNA From Specs of Blood'

marked for identification during nanogram discussion

Defendants' Exhibit 2184

Hand-drawn diagram by Blasier illustrating RFLP window sizing concept

marked for identification during window-size argument

Informal

The sock — 1 in 530 billion five-probe RFLP match, sizing sheets requested

discussed; Cotton searching for sizing sheet at recess

Notable Exchanges (3)

Robert Blasier•Robin Cotton

Blasier repeatedly cuts Cotton off mid-answer with 'Thank you' when she begins to qualify her theoretical concessions, forcing the jury to hear only the bare admission. Cotton tries to clarify but Blasier moves on: 'We'll do this step by step. Okay?'

strategic

Robert Blasier•Robin Cotton

Blasier uses a 25,000-mile ladder analogy for the full DNA sequence to make the point that RFLP and PCR tests examine a vanishingly small fraction of the total genome. Cotton is willing to accept the math hypothetically but notes the base pairs are not actually half an inch apart.

pedagogical/strategic

Robert Blasier•Robin Cotton

Blasier establishes Cotton was paid approximately $1,200/day (or $200/hour for shorter blocks) for 8-9 days of work for the plaintiffs, after her criminal trial work was entirely taxpayer-funded.

revealing

Light Moments (2)

Robert Blasier

Blasier's tinker-toy analogy for base pairs gets tangled: 'You can figure out how these go together, round letters go together. A and C and G -- I'm sorry, guess you can't do that. Anyway, they only go together one way, correct?'

Robert Blasier / Robin Cotton

'I didn't do the math. It turned out to be about 25 thousand miles. Does that sound right?' / 'I haven't done the math.'

Credibility Attacks (2)

⚔ Robin Cotton

financial bias

Blasier establishes that Cotton's criminal trial work was fully funded by Los Angeles County taxpayers, while her civil trial work is compensated at $1,200/day by the plaintiffs — implying a financial interest in the outcome.

⚔ RFLP methodology

technical limitation / methodological attack

Blasier extracts a series of concessions: tests examine a tiny fraction of total DNA; five probes do not establish unique identity; the match window means 999 of 1,000 fragments within range could theoretically come from different people; measurement precision is limited by the technology itself.

Witness Demeanor

Professional and composed throughout; repeatedly attempts to qualify theoretical admissions but is cut off

Corrects Blasier's technical imprecision (spray film vs. X-ray; 46 chromosomal sections vs. 23; allele length) without apparent irritation

Searching for sizing sheets at end of examination; recess called to allow her to locate them

Objections

3 objections (2 sustained, 0 overruled)

Proceeding 8249 • 284 utterances • Plaintiff witness

Civil Trial

Department 103