Question About GSR


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kingpin008
February 26, 2009, 03:58 PM
So, I'm watching one of these CSI-type shows, and the issue of GSR (gunshot residue) comes up when the detectives start to collect evidence from one of the potential suspects.

It eventually is discovered that the GSR on the suspect's hands got there when her hands touched the back seat of the police car - the car had been used to transport the perpetrator of a gang shooting previous to her riding in it.

Anyway - I got to wondering, let's say that someone is suspected of a crime, and GSR is found on their hands, and this is used as key evidence against them. Is there any way that the residue could be tested to determine what type/brand of powder it was?

I mean, I know that there are multiple types of gun powders (single base, double base, black powder, shotgun and rifle varities, etc) that have different properties and burn rates. Would these characteristics translate to the gases once the powder is ignited during firing? And if so, would they be in large enough amounts to be measured and compared?

I know it's just TV, but it actually got me thinking this time!

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Gunship69
February 26, 2009, 06:23 PM
I don't really believe so. All a GSR kit can prove is that you shot or handle a firearm recently. I've been a cop 12 years and thats all I've ever learned. It's really not a very good source of evidence.

kingpin008
February 26, 2009, 06:46 PM
I thought as much, but wasn't entirely sure. Thanks!

rodregier
February 26, 2009, 08:53 PM
My understanding is that GSR testing is designed primarily to detect nitrates, which are associated with the decomposition products of smokeless powder or fertilizers.

This source claims the FBI has quietly discontinued GSR testing:

http://gacriminallawblog.com/2006/05/26/fbi-abandons-gun-shot-residue-gsr-testing/

They speculate it was due to potential for cross-contamination and resulting false positives.

Duke of Doubt
February 26, 2009, 08:58 PM
GSR is old and cold -- merely relieving one's self sloppily can give a false positive.

I've tried homicides, gun crimes, and all sorts of other fun stuff besides-- and I have never, ever, not only ever seen, but also have never heard, of GSR used in a criminal case in Maine, at least in recent decades. TV stuff. And believe me, we are plenty old-fashioned.

heron
February 26, 2009, 09:32 PM
I think it's theoretically possible, but there's a whole lot of that down in Alice's rabbit-hole.

To actually do it, they'd first have to collect a large enough sample to do a spectrographic analysis on, or preferably two or more such analyses. That alone says "NO." (Some of you may have heard of drug cases, wherein the prosecutors were asked where the confiscated drug evidence was, and replied that "the sample was destroyed during testing." Case dismissed for lack of evidence.

Now, assuming they were able to scrape a few grams of it off you (like if your hands were caked completely black from it), then they'd have to prove that their sample matched that from the crime. Maybe possible, but they'd have to test like samples for every powder that could conceivably be associated with the crime in question. Possible? Maybe. Practical? Very unlikely.

Ain't gonna happen (except on CSI Miami).

B yond
February 26, 2009, 10:50 PM
I don't think GSR evidence is very damning if it's ever brought up in court. A competent lawyer should be able to poke all kinds of holes in it.

At any given time I'm sure GSR could be found on me, if not on my hands then on my clothes, whether I've been shooting that day or not. A day does not go by that I don't handle a firearm before leaving the house.

I think it's comparable to hair and fiber forensics in that it's over-hyped by the entertainment industry and not as accurate, reliable, or damning as they would have you believe. It could possibly be used to rule someone out as a suspect, but I think that's about it.

Heck, fingerprints and DNA aren't even 100% like they want us to think they are.

DoubleTapDrew
February 27, 2009, 12:30 AM
Probably 95% of THR members have GSR residue on them at any given time and the number of them that had murdered someone recently is far smaller :p
On CSI they could not only tell what brand of gunpowder it was, they could tell how many grains were in the load, what rifling the pistol had, how many rounds you fired, what you had for breakfast, the last time you petted a cocker spaniel, and the name of your 3rd grade teacher. Those shows are as accurate as a rocket powered marble.

B yond
February 27, 2009, 12:33 AM
Probably 95% of THR members have GSR residue on them at any given time and the number of them that had murdered someone recently is far smaller

wait wait wait...I thought we were all GUN OWNERS? Aren't guns just for murdering people?

Officers'Wife
February 27, 2009, 12:35 AM
Please, a GSR test would show positive after you had gathered eggs or cleaned your cat's litter pan and wouldn't be able to tell if it was a handgun or chicken manure.

Ithaca37
February 27, 2009, 11:18 AM
read this article
http://www.newscientist.com/article/mg18825274.300

Duke of Doubt
February 27, 2009, 11:42 AM
Nice, Ithaca.

I can sneeze down onto a frigging Dallas sewer grate and be good for 22.XI.'63, if you buy into the "CSI" fraud. Thankfully, local judges do not carry umbrellas onto that particular grassy knoll.

eye5600
February 27, 2009, 12:26 PM
They do put tell-tale material in commercial explosives, so if you blow a save with dynamite, they'll be able to trace the batch. I've been expecting to hear that they were going to do the same thing with ammo, but it must not be feasible, even in theory. It would seem a lot easier that the microstamping, etc.

And if they did, it might make the residue easier to ID.

PTK
February 27, 2009, 12:42 PM
They do put tell-tale material in commercial explosives, so if you blow a save with dynamite, they'll be able to trace the batch

Commercial explosives generally don't have tracers in them - it didn't work very well. Military bulk explosives, however...

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