Cross-examination of Gary Sims (part 4)

📄 Cross-examination of Gary Sims (part 4) — Thursday, May 18, 1995

Address:

C:\DEPT103\CRIMINAL\1995\MAY\18\CROSS-EXAMINATION-OF-GARY-SIMS.DOC

TRIAL

▲ Day 77 of 167

◀ Sidebar: DNA sample projections Cross-examination of Gary Sims (part 5) ▶

Witness: Gary Sims
Examiner: Barry Scheck
Called by: Prosecution • Date: Thursday, May 18, 1995 • Utterances: 44

Barry Scheck continues his highly technical cross-examination of Gary Sims, walking through nanogram-level DNA quantification calculations for swatches (samples 50 and 52). The exchange focuses on whether slot-blot measurements, combined with assumptions about uniform distribution of biological material across swatches, can be used to project total DNA quantities — with Scheck trying to establish that Cellmark's DNA yields are consistent with LAPD's own measurements.

# 1 (The following proceedings were held in open court:)

# 2 MR. SCHECK:

Mr. Sims--

# 3 MR. SIMS:

Yes.

# 4 MR. SCHECK:

--in assessing samples for purposes of forensic DNA testing, is it a regular practice to take slot-blot measurements of parts of swatches?

# 5 MR. SIMS:

Well, sometimes we use slot-blots, but sometimes we quantitate just from the yield gel.

# 6 MR. SCHECK:

By either using the yield gel or a slot-blot or even a southern transfer together using these quantitative methods?

# 7 MR. SIMS:

Yes.

# 8 MR. SCHECK:

Well, is it a regular--well, is it a practice that is used to try to make a projection as to how much total DNA one would expect to find in a sample based on the assumption that the amount of DNA one sees in one part of a swatch would be randomly distributed on other parts of the swatches? Is that one way that people in your line of work try to make estimates about the amount of DNA for purposes of figuring out a testing process?

# 9 MR. SIMS:

Yes.

# 10 MR. SCHECK:

All right. And in fact at some point earlier did you go through calculations based on the methods similar to the ones we are going through here today to try to make projections as to how much DNA would be on these various swatches?

# 11 MR. SIMS:

Yes.

# 12 MR. SCHECK:

All right. May I proceed? So the assumption, for purposes of making estimates that the amount of DNA one would find on swatches would be randomly distributed, is the kind of assumption forensic DNA analysts such as yourself make when trying to make reasonable projections about what exists on samples?

# 13 MR. SIMS:

Yes.

# 14 MR. SCHECK:

May I proceed, your Honor?

# 15 THE COURT:

Proceed.

# 16 MR. SCHECK:

I forget, I'm sorry, it is painstaking, but what are we up to? 50?

# 17 MR. SIMS:

I think we are on 50.

# 18 MR. SCHECK:

Only two more.

# 19 MR. SIMS:

Excuse me.

# 20 MR. SCHECK:

Let us assume--you--your slot-blot estimate was 1.94 nanograms.

# 21 MR. SIMS:

That sounds correct.

# 22 MR. SCHECK:

If you assume that you extracted 16 percent of the total sample--

# 23 MR. HARMON:

Objection, improper hypothetical.

# 24 THE COURT:

Overruled.

# 25 MR. SCHECK:

--would you project that the total human DNA in the sample would be about 12.1 nanograms?

# 26 MR. HARMON:

Objection, it is irrelevant.

# 27 THE COURT:

Overruled.

# 28 MR. SIMS:

Yes.

# 29 MR. SCHECK:

And let's make it easy on sample 52. Umm--well, I might have asked this before. Let's try it this way: If Robin Cotton had testified that the amount of human DNA that was used for the RFLP testing at Cellmark for sample 52 was 25 nanograms of human DNA, would that be consistent with your calculations that--with your slot-blot of 3.64 nanograms based on the assumption that you had 11.5 percent of the sample?

# 30 MR. HARMON:

Objection, calls for hearsay. It misstates Dr. Cotton's testimony.

# 31 THE COURT:

Sustained.

# 32 MR. SCHECK:

All right.

# 33 MR. SCHECK:

If you assume that you had 11.5 percent of the total sample, and taking into consideration that your slot-blot was 3.64 nanograms, would the total amount of human DNA in sample 52 be something on the order of 31.6 nanograms?

# 34 MR. HARMON:

Objection, improper hypothetical.

# 35 THE COURT:

Sustained as stated.

# 36 MR. SCHECK:

All right.

# 37 THE COURT:

You forgot the assumption about uniformity.

KEY QUOTE

# 38 MR. SCHECK:

Yes, I assumed that.

# 39 MR. SCHECK:

Assuming of course in this projection that the biological specimen was uniformly--randomly distributed over the swatches.

# 40 MR. SIMS:

Okay.

# 41 MR. SCHECK:

Is that right?

# 42 MR. SIMS:

Okay. Well, can I do the calculation now?

# 43 MR. SCHECK:

Do it.

# 44 MR. SIMS:

I want to take a minute with this one.

KEY QUOTE

Temperature

procedural

Key Quotes (3)

Lance A. Ito

You forgot the assumption about uniformity.

The judge himself corrects Scheck's hypothetical mid-examination, prompting Scheck to restate it properly — an unusual intervention that underscores how technically exacting this line of questioning was.

Gary Sims

I want to take a minute with this one.

Sims asks to pause and actually perform the calculation live — signals the math is non-trivial and the question is substantive, not just rhetorical.

Barry Scheck

Only two more.

Reveals the tedious, item-by-item nature of this examination — Scheck is methodically working through a numbered list of samples.

Evidence (3)

Informal

Sample 50 — slot-blot estimate of 1.94 nanograms; Scheck projects ~12.1 ng total DNA assuming 16% extraction

discussed, calculated

Informal

Sample 52 — slot-blot of 3.64 nanograms; Scheck attempts to project ~31.6 ng total DNA assuming 11.5% extraction

discussed, calculated

Informal

Cellmark RFLP testing — Robin Cotton's testimony that 25 nanograms of human DNA was used for sample 52

referenced (objection sustained as hearsay/misstatement)

Notable Exchanges (2)

Barry Scheck•Lance A. Ito

Judge Ito interrupts to note Scheck omitted the uniformity assumption from his hypothetical — Scheck incorporates the correction and re-asks

corrective, unusually collaborative

Barry Scheck•Gary Sims

Sims asks to pause to actually do the math on sample 52 live; Scheck simply says 'Do it'

measured, deliberate

Light Moments (1)

Barry Scheck

Scheck loses track of which sample number they're on and has to ask Sims — 'I forget, I'm sorry, it is painstaking, but what are we up to? 50?'

Credibility Attacks (1)

⚔ Gary Sims

internal inconsistency / calculation challenge

Scheck uses Sims's own slot-blot measurements against projected total DNA yields, implying the quantities are consistent with Cellmark's findings — undercutting any suggestion the samples were degraded or insufficient

Objections

4 objections (2 sustained, 2 overruled)

Proceeding 6097 • 44 utterances • Prosecution witness

Criminal Trial

Department 103