Recross-examination of Greg Matheson

📄 Recross-examination of Greg Matheson — Friday, July 8, 1994

Address:

C:\DEPT103\PRELIMINARY\1994\JUL\8\RECROSS-EXAMINATION-OF-GREG-MA.DOC

TRIAL

▲ Day 6 of 6

◀ Redirect examination of Greg Matheson New witness sworn in ▶

Witness: Gregory Matheson
Examiner: Gerald Uelmen
Called by: Prosecution • Date: Friday, July 8, 1994 • Utterances: 24

Defense attorney Uelmen asked Matheson two brief lines of questioning: first, whether a foreign blood subtype could be masked in a mixture if diluted sufficiently (Matheson acknowledged the ABO result might still appear even when the PGM subtype disappears); second, how much of the crime scene swatches and OJ Simpson's blood sample was consumed during testing. Matheson provided specific measurements for both, confirming sample inventory was tracked.

# 1 THE COURT:

Mr. Uelmen, anything further?

# 2 MR. UELMEN:

Yeah. Thank you.

# 3

RECROSS-EXAMINATION

# 4

BY mr. uelmen:

# 5 Q:

Mr. Matheson, if we had a mixture that included pgm subtype 2+2- plus some other subtype, at some point, in terms of the ratio of the mixture, the other subtype would be masked and would not appear in your results; isn't that correct?

# 6 A:

this is similar to what we were talking about for -- if there was a completely foreign type besides 2+ or 2-?

# 7 Q:

Right.

# 8 A:

If you got to the point other blood was diluted to the point it didn't show up, you would still see it.

# 9 Q:

But you would still see the a result on the abo test?

# 10 A:

I suppose at some point it is possible where you would still see the a and not the subtype.

KEY QUOTE

# 11 MR. UELMEN:

Thank you. Nothing further. Excuse me. One moment.

# 12 Q:

Do you make some sort of calculation as to how much of the sample you are consuming in the course of the tests that you are running?

# 13 A:

Are you asking me can I tell you how much I used?

# 14 Q:

YES.

# 15 A:

Yes, I can. Referring to my analysis notes, I consumed a portion of one of the swatches that was available to me that was approximately 6 millimeters by 3. Approximation. That left two swatches plus a portion of that one remaining that I worked on.

# 16 Q:

So each of these tests that you perform consumes a certain proportion of the sample that you have available to test?

# 17 A:

Yes, that's correct.

# 18 Q:

OKAY.

# 19 MR. UELMEN:

I'm sorry, your Honor. One other question.

# 20 THE COURT:

All right.

# 21

BY mr. uelmen:

# 22 Q:

With respect to the sample of the item No. 17, the blood of O.J. Simpson, did you similarly inventory how much of that sample you consumed?

# 23 A:

The proportion that would be consumed would have been, oh, a stain of -- well, consisting of significantly less than one drop out of the vial, which, when I received it, had about 2 milliliters of blood in it. So it would have been an insignificant quantity to the amount that was present.

KEY QUOTE

# 24 MR. UELMEN:

Thank you.

Temperature

procedural

Key Quotes (3)

Greg Matheson

I suppose at some point it is possible where you would still see the a and not the subtype.

Concedes that ABO typing and PGM subtyping can decouple in diluted mixtures, leaving open the possibility that a foreign contributor's subtype could be masked while the ABO result still shows.

Greg Matheson

I consumed a portion of one of the swatches that was approximately 6 millimeters by 3. Approximation. That left two swatches plus a portion of that one remaining that I worked on.

Establishes precisely how much crime scene sample was consumed in testing, relevant to chain of custody and remaining sample availability for defense testing.

Greg Matheson

The proportion that would be consumed would have been, oh, a stain of -- well, consisting of significantly less than one drop out of the vial, which, when I received it, had about 2 milliliters of blood in it.

Quantifies consumption from OJ Simpson's reference blood vial — a vial that later became central to defense claims about missing blood volume.

Evidence (2)

Informal

Crime scene blood swatches — Matheson consumed approximately a 6mm x 3mm portion, leaving two full swatches plus a partial

discussed

Item No. 17

OJ Simpson's reference blood vial, received with approximately 2 milliliters of blood

discussed

Notable Exchanges (2)

Gerald Uelmen•Greg Matheson

Uelmen established that PGM subtyping can fail to detect a foreign blood contributor if their contribution is sufficiently diluted, while ABO typing may still register — creating a theoretical gap in mixture analysis.

strategic

Gerald Uelmen•Greg Matheson

Uelmen pinned down exactly how much of the reference blood sample was consumed, setting up future arguments about the volume of blood unaccounted for in Simpson's reference vial.

strategic

Objections

None recorded

Proceeding 8990 • 24 utterances • Prosecution witness

Preliminary Trial

Department 103