📄 Cross-examination of Dr. Bruce Weir (afternoon, part 1) — Monday, June 26, 1995
Address:
C:\DEPT103\CRIMINAL\1995\JUN\26\CROSS-EXAMINATION-OF-DR-BRUCE-.DOC
TRIAL
▲ Day 103 of 167

Cross-examination of Dr. Bruce Weir (afternoon, part 1)

Witness: Dr. Bruce Weir
Examiner: Peter Neufeld
Called by: Prosecution • Date: Monday, June 26, 1995 • Utterances: 48
Defense attorney Peter Neufeld continued cross-examining DNA statistics expert Dr. Bruce Weir on the afternoon of June 26, 1995, focusing on how to calculate the percentage of the population that could be excluded as contributors to DNA mixtures found on evidence items. The central dispute was methodological: Neufeld argued for using the NRC report's single-locus approach (which produced a more inclusive, less discriminating statistic), while Weir insisted his multi-locus calculations were correct and that Neufeld was presenting 'only half the story.' The session ends mid-calculation as they move toward analyzing items 303, 304, and 305.
1 (The following proceedings were held in open court, in the presence of the jury:)
2 THE COURT:

All right. Thank you, ladies and gentlemen. Please be seated. All right. Let the record reflect we have been rejoined by all the members of our jury panel. Good afternoon, ladies and gentlemen.

THE JURY: Good afternoon.

3 THE COURT:

Dr. Weir, would you resume the witness stand, please.

Bruce Weir, the witness on the stand at the time of the lunch recess, resumed the stand and testified further as follows:

4 THE COURT:

All right. Good afternoon again, doctor.

5 DR. WEIR:

Good afternoon, your Honor.

6 THE COURT:

Mr. Neufeld.

7 MR. NEUFELD:

Thank you.

CROSS-EXAMINATION (RESUMED) BY MR. NEUFELD

8 MR. NEUFELD:

Dr. Weir, just so we can explain this--these fractions a little bit to the Court and to the ladies and gentlemen of the jury, for instance, taking item no. 29, when I show that fraction 1 over 2, doesn't that mean that approximately 50 percent of the population could not be excluded as a potential contributor to the mixture reflected on the steering wheel stain? Is that what 1 over 2 means?

9 DR. WEIR:

That's what that says. It doesn't allow us to interpret the mixture however.

10 MR. NEUFELD:

But that is what it says, sir; is that correct?

11 DR. WEIR:

That's what it says, yes.

12 MR. NEUFELD:

Thank you. Now, what I would like you to do, sir, is I'm going to also ask you to do--using the same approach that we utilized for item no. 29, I'm going to ask you to do the same thing for item 303, which is 304 and 305 as well as well as G10. And to do that, sir, again, referring to the databases that you received in this case, the database from Cellmark and then the database for D1S80--

13 DR. WEIR:

Excuse me, Mr. Neufeld. I have used FBI's data on the polymarker--on the PCR.

14 MR. NEUFELD:

On the D1S80. But I also showed you, as you may recall, Cellmark's tables for the data on DQ-Alpha; is that correct?

15 DR. WEIR:

That's right. So we're not only doing different calculations, we're using different databases.

16 MR. NEUFELD:

All right. Well--

17 (Brief pause.)
18 MR. NEUFELD:

Well, you remember that the DQ-Alpha calculations that you relied on--that you relied on for arriving at that NRC number was Defendant's 1201. I'll just show it again to you to refresh your recollection, sir.

19 DR. WEIR:

Yes. Your calculations are Cellmark databases and mine are FBI.

20 MR. NEUFELD:

Okay. But I think you said frankly that it shouldn't make much difference or the difference should be rather minimal for these DQ-Alpha frequencies whether one uses the FBI's database or the Cellmark database; is that correct?

21 DR. WEIR:

They won't be greatly different, but they won't be the same.

22 MR. NEUFELD:

Okay. But I want to--since we already did the calculation for item 29 using Cellmark's database and since Cellmark did report DQ-Alpha typing results in this case, I'm going to ask you to use Cellmark's table again, and then, of course, for the D1S80, you would use the FBI's databases since Cellmark doesn't have any databases for D1S80. Item 303, 304 and 305 has been typed, has it not, referring to People's exhibit 260, both on the DQ-Alpha locus and also on the D1S80 locus; is that correct, sir?

23 DR. WEIR:

Yes, that's right.

24 MR. NEUFELD:

Okay. So one could--so if one wanted to answer the question, that is the same question that is posed in the NRC report, which is what percentage of the population cannot be excluded as being a potential contributor to this mixture, namely, the mixture on the console of 303, 304 and 305, one could make certain calculations and generate certain sums for the DQ-Alpha locus and then again for the D1S80 locus and then you would combine those; is that correct, sir?

25 DR. WEIR:

Yes. You've just pointed out something in fact, that we didn't do that of course here. We've only done the one locus. What--my figures are on all the loci. Yours are just on the one locus.

26 MR. NEUFELD:

For the--for the 303, 304 and 305 there?

27 DR. WEIR:

The 303, 304 and 305 is typed, the DQ-Alpha and D1S80. The figures I've given are typed based on both loci. You've only given half the story.

28 MR. NEUFELD:

Right. Okay.

29 DR. WEIR:

So it's even more misleading than I had realized.

KEY QUOTE
30 MR. NEUFELD:

Well, on item 29, there is only one locus; isn't that correct? I'm sorry. Withdrawn. There are polymarkers in the DQ-Alpha locus; isn't that right?

31 DR. WEIR:

That's--that's right. So there were six loci. And I've given a six-locus result and you've given a one-locus result.

32 MR. NEUFELD:

Well, excuse me, sir. But for item 29, isn't it true that the polymarkers do not discriminate, the polymarker results themselves?

33 DR. WEIR:

I'll need--I'm not sure that's true. Let's just go and look.

34 MR. NEUFELD:

Well, let me ask you the question specifically, sir. Isn't it true that a hundred percent of the population is reflected in those polymarker results alone?

35 DR. WEIR:

I think--I think finally we've put our finger on our main difference. To calculate the frequency of a mixture, I take the mixtures of people and then the correct method that does not sum to a hundred percent. Your method does. So we've got them on the same piece of paper and we're talking about very different things.

KEY QUOTE
36 MR. NEUFELD:

I'm not talking about my methods. I'm talking about the NRC method, Dr. Weir. And what I'm asking you is, applying the NRC method to item 29, would you agree that there is no--there's no one in the population who could not be included or who wouldn't be included as a potential contributor to the polymarker profile that you see for item 29?

KEY QUOTE
37 DR. WEIR:

I think that's the point. That's why it's so absurd.

KEY QUOTE
38 MR. NEUFELD:

Do you agree with that?

39 DR. WEIR:

Yes, I do.

40 MR. NEUFELD:

Thank you. And would you agree, sir, that the one genetic system where there is some portion of the population who would be excluded is for the DQ-Alpha system in item 29?

41 DR. WEIR:

Only if you mean excluded meaning single people. For the mixtures, of course, we've got several people.

42 MR. NEUFELD:

Right. I'm talking about single people who could be excluded saying that there's some people who just could not have been a contributor to this mixture.

43 DR. WEIR:

So the question--I think I'm agreeing with you, yes.

44 MR. NEUFELD:

Okay. Fine. Now, here's what I'm asking you, sir. For items 303, 304 and 305, if we use that NRC method and we use the D1S80 databases from the FBI and we use the DQ-Alpha databases that Cellmark used in doing their own calculations for 303, 304 and 305--

45 MR. NEUFELD:

And this would be 120--

46 THE COURT:

9.

47 MR. NEUFELD:

1209?

48 (Deft's 1209 for id = table)

Temperature

tense

Key Quotes (4)

Dr. Bruce Weir
So it's even more misleading than I had realized.
Weir's pointed response after realizing Neufeld's calculations for items 303/304/305 used only one locus while Weir's used all typed loci — a rare moment of sharpness from the witness directed at defense counsel's framing.
Dr. Bruce Weir
I think finally we've put our finger on our main difference. To calculate the frequency of a mixture, I take the mixtures of people and then the correct method that does not sum to a hundred percent. Your method does.
Weir identifies the core methodological disagreement: the NRC single-contributor approach (Neufeld's) sums to 100% and is therefore uninformative, while Weir's mixture method does not — a key distinction the defense was trying to obscure.
Dr. Bruce Weir
I think that's the point. That's why it's so absurd.
Weir concedes that under Neufeld's preferred NRC method, 100% of the population cannot be excluded from the polymarker profile on item 29 — but frames this as proof the NRC method is the wrong tool for mixture analysis, not as a concession to the defense.
Peter Neufeld
I'm not talking about my methods. I'm talking about the NRC method, Dr. Weir.
Neufeld deflects Weir's criticism by attributing the contested approach to the authoritative NRC report rather than to himself, attempting to legitimize a framing Weir has repeatedly called misleading.

Evidence (3)

People's 260
DNA typing results for items 303, 304, and 305 (Bronco console stain), showing both DQ-Alpha and D1S80 locus results
discussed
Defendant's 1201
Cellmark's DQ-Alpha frequency database tables, used by Neufeld for his NRC-method calculations
discussed
Defendant's 1209
Table (likely DQ-Alpha or D1S80 data for items 303/304/305); marked for identification at end of session
introduced for identification

Notable Exchanges (2)

Peter NeufeldDr. Bruce Weir
Neufeld walks Weir through the NRC method applied to item 29 (steering wheel stain), eliciting the admission that the polymarker results alone include 100% of the population. Weir agrees but uses this admission to argue the method is 'absurd' for mixture analysis — a Pyrrhic concession.
strategic
Peter NeufeldDr. Bruce Weir
Weir corrects Neufeld mid-examination by pointing out that for items 303/304/305, Neufeld presented only one-locus data while Weir's statistics incorporated all typed loci, calling Neufeld's presentation 'even more misleading than I had realized.' Neufeld responds with 'Right. Okay.' and moves on.
revealing

Credibility Attacks (1)

⚔ Dr. Bruce Weir
methodological challenge
Neufeld repeatedly pushed Weir to apply the NRC report's recommended method instead of Weir's own mixture-frequency approach, framing Weir's multi-locus statistics as non-standard and attempting to substitute a method that produces far less discriminating (and therefore less damning) numbers for the defense.

Witness Demeanor

(Brief pause.) — during database discussion

Objections

None recorded
Proceeding 6546 • 48 utterances • Prosecution witness
Criminal Trial
Department 103
⚖️ Start
📂 JUN 26, 1995 📄 Cross-examination of Dr. Bruce
JUN 26, 1995 KRT DvH TD