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DNA and GSR Update on George Zimmerman Case

Cross posted from Frederick Leatherman Law Blog

Summary of DNA and GSR Evidence*

A DNA Double-Helix

Image by Keith Ramsey

1. Trayvon Martin’s shirt (ME-8)

Four stains tested positive for blood. Trayvon Martin is the source of two stains. George Zimmerman is the source for another and the fourth stain is a mixed sample containing DNA from both individuals.

2. Trayvon Martin’s hoodie (ME 12)

Two stains test positive for blood. Trayvon is the source of one and no DNA result on the other.

No DNA results foreign to Trayvon Martin are found on both lower sleeves.

Two holes were discovered in the area of the “upper left chest” (one in each item of clothing) that exhibited characteristics consistent with a contact gunshot.

3. My thoughts

Given the lack of George Zimmerman’s DNA on the hoodie, the presence of blood contributed by George Zimmerman on the shirt that he was wearing underneath the hoodie indicates the hoodie was not covering the portion of the shirt where the bloodstain was located. Difficult to draw any additional conclusions without knowing the location of the bloodstains on the shirt (e.g., whether the hoodie was pulled up exposing the shirt or the shirt was extended below the hoodie or how this could have happened)

No DNA results foreign to Trayvon Martin are found on both lower sleeves suggesting that Trayvon was not beating Zimmerman.

The two holes obviously came from the same shot and there is a potential conflict between the location of the wound (1 inch left of the midline and 1/2 inch below the nipple) and the location of the two holes (upper chest area).

There also is a potential conflict created by the medical examiner’s conclusion that the muzzle of the gun was 2 to 4 inches away (an intermediate distance) when the fatal shot was fired compared the firearm’s analyst who concluded that the muzzle of the gun was in contact with the clothing.

Marilyn, who comments at my law blog, suggested Zimmerman was restraining Martin by gripping his clothing with one hand and fired the gun with the other as Martin was attempting to get away. This could explain how the upper part of both items of clothing could have been pulled down as well as a few inches away from Martin’s chest when Zimmerman fired the fatal shot. It also might explain how Zimmerman’s blood might have gotten on the shirt, but not the hoodie.

I think we lack sufficient evidence to draw that conclusion at this point, but it’s certainly possible. Might also explain how the shot went straight in without angling up or down, left or right.

Of course, if it happened this way, the shooting definitely was not in self-defense.

4. George Zimmerman’s shirt (DMS-16) and jacket (DMS-19).

Gunshot Residue (GSR) was found on the jacket in the form of 1 particle of lead found on the upper back portion of the right sleeve.

Twelve bloodstains on the shirt were contributed by George Zimmerman, according to DNA analysis.

Thirteen bloodstains on the jacket contain Zimmerman’s DNA. Trayvon Martin’s DNA is present in four of them (mixed samples) and his DNA was detected in one mixed sample where the other contributor could not be identifies.

5. My thoughts

We do not know the size of any of these bloodstains. but I imagine some are quite small because they probably were deposited by high velocity blood spatter from the gunshot, which resembles a fine spray.

The pattern of blood spatter may establish where the wound was in relation to the jacket when the fatal shot was fired and help to establish the relative positions of the two individuals.

The only conclusion one can draw regarding the presence of GSR is that the object in question was in a shooting environment at some time.

GSR can be wiped or washed off, and one cannot tell how long it has been present, so we probably cannot reliably draw any conclusions from the presence of the single particle of lead on the upper back portion of the right sleeve of his jacket.

*The information in this article comes from the lab reports in the document dump.

1. Lab Report March 26, 2012 (p. 104)

2. Supplementary Lab Report May 9, 2012 (p. 110)

3. Lab Report March 22, 2012 (p. 122)

4. Lab Report March 28, 2012 (p. 124)

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Frederick Leatherman

Frederick Leatherman

I am a former law professor and felony criminal defense lawyer who practiced in state and federal courts for 30 years specializing in death penalty cases, forensics, and drug cases.

I taught criminal law, criminal procedure, law and forensics, and trial advocacy for three years after retiring from my law practice.

I also co-founded Innocence Project Northwest (IPNW) at the University of Washington School of Law in Seattle and recruited 40 lawyers who agreed to work pro bono, assisted by law students, representing 17 innocent men and women wrongfully convicted of sexually abusing their children in the notorious Wenatchee Sex Ring witch-hunt prosecutions during the mid 90s. All 17 were freed from imprisonment.

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