Redirect examination of Dr. Renee Shields (1)

📄 Redirect examination of Dr. Renee Shields (1) — Thursday, June 22, 1995

Address:

C:\DEPT103\CRIMINAL\1995\JUN\22\REDIRECT-EXAMINATION-OF-DR-REN.DOC

TRIAL

▲ Day 101 of 167

◀ Redirect examination of Dr. Renee Shields Re-redirect examination of Dr. Renee Shields ▶

Witness: Dr. Renee Shields
Examiner: George Clarke
Called by: Prosecution • Date: Thursday, June 22, 1995 • Utterances: 48

Defense attorney Thompson conducted a brief redirect of DNA statistics expert Dr. Renee Shields, focusing on her superior qualifications in molecular biology compared to prosecution expert Dr. Weir, and reinforcing her critique that Dr. Weir's statistical calculations for mixed bloodstains (particularly item 78) were scientifically inappropriate. Thompson also elicited testimony about two prior cases — one in Minnesota and one in northern California — where similar mixture statistics were withdrawn by prosecutors after defense challenges became apparent, suggesting a pattern of prosecutorial overreach in DNA mixture statistics.

# 1 MR. THOMPSON:

Just a few, your Honor.

REDIRECT EXAMINATION BY MR. THOMPSON

# 2 MR. THOMPSON:

Okay. Dr. Weir--excuse me. Dr. Shields, you were asked about your qualifications relative to Dr. Weir's in various areas. Which of the two of you is more qualified in the area of molecular biology?

# 3 DR. SHIELDS:

I am.

# 4 MR. THOMPSON:

Okay. And which of the two of you do you think is more qualified with regard to drawing logical inferences from data produced by molecular biological techniques?

# 5 DR. SHIELDS:

I think we're probably about equally qualified. I know he's convinced me of some things. I think we've come to the same conclusions a number of times.

# 6 MR. THOMPSON:

Okay. Now, Mr. Clarke asked you a number of questions about the assumption regarding the number of contributors that's part of Dr. Weir's computations. Does Dr. Weir also make additional assumptions concerning things like whether alleles are observed and not observed in the stain?

# 7 DR. SHIELDS:

Not in 29, but in 78, yes.

# 8 MR. THOMPSON:

Okay. And so is that an additional assumption that is important in how Dr. Weir computes those numbers?

# 9 DR. SHIELDS:

Yes. It's absolutely necessary.

# 10 MR. THOMPSON:

Okay. And are you con--do you think that there's an adequate scientific foundation for the assumptions that Dr. Weir was making with regard to item 79 or 78?

# 11 DR. SHIELDS:

No, I don't.

# 12 MR. THOMPSON:

Okay. Now--

# 13 DR. SHIELDS:

I do--well--

# 14 MR. THOMPSON:

Please continue.

# 15 DR. SHIELDS:

On item 78, there's a good match between one of the victims and that stain, and I believe that that's good information. I think that Cellmark declared that inconclusive, and most people, when there's an inconclusive, don't try to do statistics on what's left.

# 16 MR. THOMPSON:

Okay. So do you think that the kind of statistical conclusions that Dr. Weir computed in connection with item 78 are scientifically valid?

# 17 DR. SHIELDS:

Valid is an interesting term when you're talking about this sort of thing. It follows from his assumptions.

# 18 MR. THOMPSON:

Yeah. Let me ask--

# 19 DR. SHIELDS:

I don't think it's appropriate.

# 20 MR. THOMPSON:

All right. That was my next question. So you think it's inappropriate?

# 21 DR. SHIELDS:

It is valid, but inappropriate.

KEY QUOTE

# 22 MR. THOMPSON:

Okay. Now, I wanted to ask you a little bit more about this case you mentioned in Minnesota where statistics were offered in connection with mixtures and then withdrawn. Can you tell us why the statistics were withdrawn, if you know?

# 23 DR. SHIELDS:

I don't know for sure.

# 24 MR. THOMPSON:

Okay. Now, do you know of any other case where statistics were offered in connection with mixtures and then later withdrawn?

# 25 DR. SHIELDS:

Yes.

# 26 MR. CLARKE:

Objection. Irrelevant.

# 27 THE COURT:

Overruled.

# 28 MR. THOMPSON:

Okay. Can you tell us about that?

# 29 DR. SHIELDS:

That case was a case in northern California, the Defendants' names were Heronus and Burch, and they were mixtures in which people were attempting to develop frequencies based on the assumption that you would know which of four bands came from which of two defendants without any evidence to back up that you could know that. And under those circumstances, there were discussions about how one should handle that, and in essence, it ended up being withdrawn.

# 30 MR. THOMPSON:

Was this a case in which the Defense was preparing to challenge those kinds of statistical computations?

# 31 DR. SHIELDS:

Yes.

# 32 MR. THOMPSON:

And was the evidence drawn after it became apparent to the Prosecution such a challenge was forthcoming?

# 33 DR. SHIELDS:

On the basis of a letter from the Prosecutor in that case, yes.

KEY QUOTE

# 34 MR. THOMPSON:

Okay. Which laboratory was involved in this case in Minnesota?

# 35 DR. SHIELDS:

The FBI.

# 36 MR. THOMPSON:

Okay. Does the--in the FBI's protocol, is there a section that describes how--

# 37 DR. SHIELDS:

It was the FBI's database. It was Minnesota.

# 38 MR. THOMPSON:

Okay. So it was the Minnesota lab--

# 39 DR. SHIELDS:

Bureau of Criminal Apprehension.

# 40 MR. THOMPSON:

Are you aware of any forensic laboratories that as part of their protocol have a discussion of how to compute statistics in the case of mixtures?

# 41 DR. SHIELDS:

No.

# 42 MR. THOMPSON:

Okay. What--to--in your understanding, what do labs generally do when confronted with a--say a mixed bloodstain?

# 43 DR. SHIELDS:

I can only base it on the three cases of where I've seen that, four cases. And what they will do is, they will end up providing a statistic that's associated with--they will say that someone's not excluded and they will provide then the frequency of the pattern that is the person who is not excluded's rather than the frequency of the individuals who would not be excluded.

# 44 MR. THOMPSON:

Okay. One moment, your Honor.

# 45 MR. THOMPSON:

Dr. Shields, have you changed your mind about the appropriateness of Dr. Weir's calculations as a result of any other questions Mr. Clarke has asked you?

# 46 DR. SHIELDS:

No.

# 47 MR. THOMPSON:

Okay. Thank you.

# 48 MR. THOMPSON:

No further questions.

Temperature

procedural

Key Quotes (4)

Dr. Renee Shields

It is valid, but inappropriate.

A precise and memorable formulation of her critique — she acknowledges Dr. Weir's math follows from his assumptions while maintaining those assumptions themselves are scientifically unjustified for mixed stains.

Dr. Renee Shields

Cellmark declared that inconclusive, and most people, when there's an inconclusive, don't try to do statistics on what's left.

Directly attacks the foundation of Dr. Weir's statistics on item 78 — if the lab itself called the result inconclusive, computing probabilities from it is methodologically improper.

Dr. Renee Shields

No, I don't.

Flat denial that there is adequate scientific foundation for Dr. Weir's assumptions on item 78 — delivered without qualification or hedging.

Dr. Renee Shields

On the basis of a letter from the Prosecutor in that case, yes.

Confirms that in the California Heronus/Burch case, the prosecution withdrew its mixture statistics after a defense challenge was anticipated — implying strategic rather than scientific withdrawal.

Evidence (2)

Informal

Item 78 — mixed bloodstain, declared inconclusive by Cellmark, subject of Dr. Weir's disputed statistical calculations

discussed

Informal

Item 29 — bloodstain referenced in contrast to item 78 regarding Dr. Weir's assumptions about observed/unobserved alleles

discussed

Notable Exchanges (2)

Mr. Thompson•Dr. Renee Shields

Thompson walks Shields through the 'valid but inappropriate' distinction — she initially hesitates mid-answer, Thompson encourages her to continue, and she lands on a carefully calibrated formulation that serves the defense without overstating her position.

strategic

Mr. Thompson•Dr. Renee Shields

Thompson elicits the Heronus/Burch case in northern California where mixture statistics were withdrawn after defense challenge — establishing a precedent pattern that implicitly critiques Dr. Weir's testimony in this case.

revealing

Credibility Attacks (1)

⚔ Dr. Weir

methodological critique / prior-case pattern

Shields reaffirms that Dr. Weir's statistical assumptions for mixed stains lack scientific foundation, and Thompson establishes through her testimony that similar statistics have been withdrawn in at least two other cases when challenged — casting doubt on the reliability of this type of analysis generally.

Objections

1 objections (0 sustained, 1 overruled)

Proceeding 6518 • 48 utterances • Prosecution witness

Criminal Trial

Department 103