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For LEOs? Powder residue test?
- Thread starter nswgru1
- Start date
I got home and dusted off the manuals. When you do a GunShot Residue Test, you're looking for primer residue on hands. Primer residue is barium salts, antimony and lead.
There is a time limit for collecting residue from living tissue -- around four-to-six hours.
A mild nitric acid solution is placed on swabs. The first swab goes into the vial unused as a control.
One or two swabs are used on the right hand, paying particular attention to the index finger from the knuckle to the first joint, but make sure you swab the hand thoroughly.
The swab is placed into a vial and marked. Two vials are used if two swabs are used.
The same is done for the left hand.
Unfired ammunition should be collected for comparison.
A negative GunShot Residue Test does not mean that the subject has not fired a weapon, or that weapon.
LawDog
There is a time limit for collecting residue from living tissue -- around four-to-six hours.
A mild nitric acid solution is placed on swabs. The first swab goes into the vial unused as a control.
One or two swabs are used on the right hand, paying particular attention to the index finger from the knuckle to the first joint, but make sure you swab the hand thoroughly.
The swab is placed into a vial and marked. Two vials are used if two swabs are used.
The same is done for the left hand.
Unfired ammunition should be collected for comparison.
A negative GunShot Residue Test does not mean that the subject has not fired a weapon, or that weapon.
LawDog
The negative test simply means that no residue was found on the hands. This could mean that the subject was wearing gloves when he/she fired the weapon, it may mean that they've gotten their hands into something that removed the residue or it may mean that a significant amount of time has elapsed and the residue has worn off.
Tests on a dead subject can be done after a greater amount of lapsed time after the shooting event since the dead body isn't perspiring, shedding skin cells or doing activities which remove the residue.
Assuming that the corpse became a corpse during the shooting event, if there is intact skin present on the hands of the cadaver then the GunShot Residue Test can be conducted. If the subject shuffled off this mortal coil six hours or more after doing the shooting, then the test probably won't show anything.
As far as the accuracy goes, I would imagine that the test is as accurate as any other chemical test to determine the presence of barium, antimony and/or lead.
LawDog
Tests on a dead subject can be done after a greater amount of lapsed time after the shooting event since the dead body isn't perspiring, shedding skin cells or doing activities which remove the residue.
Assuming that the corpse became a corpse during the shooting event, if there is intact skin present on the hands of the cadaver then the GunShot Residue Test can be conducted. If the subject shuffled off this mortal coil six hours or more after doing the shooting, then the test probably won't show anything.
As far as the accuracy goes, I would imagine that the test is as accurate as any other chemical test to determine the presence of barium, antimony and/or lead.
LawDog
A negative GunShot Residue Test does not mean that the subject has not fired a weapon, or that weapon.
And a positive test does not mean that they did. But it would be pretty incriminating to the unsophisticated juror.
And a positive test does not mean that they did.
The newest GSR tests measure the ratio of barium to antimony to lead, the presence and amount of other chemical traces in the residue and graph a three-dimensional picture of the GSR particles for comparison. Not only will a GSR indicate that a gun was fired by the person, but it can indicate what brand of ammunition was fired.
LawDog