GUN SHOT RESIDUE. What is Gun Shot Residue? Tiny particles of primer and gunpowder (gunshot residue...
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Transcript of GUN SHOT RESIDUE. What is Gun Shot Residue? Tiny particles of primer and gunpowder (gunshot residue...
GUN SHOT RESIDUE
What is Gun Shot Residue? Tiny particles of
primer and gunpowder (gunshot residue or GSR) are expelled from the front of the gun and from the breechblock area when the gun is fired
What is Gun Shot Residue? The further
gunshot residues travel from the muzzle, the broader and less concentrated the pattern becomes.
How is GSR detected? Primer is generally made up of barium
nitrate and antimony sulfide Most GSR detection techniques concentrate on
barium and antimony
How is GSR detected?GSR Chemical Tests
Griess Test. Will not interfere with later tests for lead residues Detect the presence of nitrite residues Primary test used by forensic investigators
How is GSR detected?GSR Chemical Tests
The Griess Test
How is GSR detected?GSR Chemical Tests
Sodium Rhodizonate Test Determines if lead residues are present
on the exhibit.
How is GSR detected?Entomology
Examiners can extract GSR from the larvae that had been feasting on the body of someone involved in, or that was in proximity to a shooting
Can GSR Convict Someone?
All the shooter has to do is wash his hands thoroughly, although normal human movement and activity can dislodge the particles even if he can’t get to a sink Most labs will not test samples collected more
than 6 hours after the shooting
Shooter’s hands are bagged
Can GSR Convict Someone? Barium and antimony can
also be found in firecrackers, paint, and some industrial settings
Too many other factors involved—weather (including wind), sweating skin, dry skin, putting hands in pockets, washing
Can GSR Convict Someone? The FBI is no longer
analyzing gunshot residue in its investigations
It could become a weapon for defense attorneys in pending cases and in efforts to overturn convictions May 26, 2006
Distance Determinations
GSR on Garments
Clothing Distance Determinations Entrance Holes:
Typically have very even margins Smaller in diameter than the bullet due
to the elasticity of the fabric
Clothing Distance Determinations
Clothing Distance Determinations Exit Holes:
Usually provide no evidence Usually wider than the actual diameter of the
bullet
GSR Deposits GSR travels 3-5 feet in most firearms At the 3-5 foot range the gunshot residues may
only consist of a few trace particles At around 18-24 inches most firearms will start to
deposit considerable concentrations of GSR At distances of less than 12 inches heavy
concentrations of visible gunshot residues will normally be deposited
GSR Deposits GSR is not readily water soluble and
clothing left exposed to the elements will not usually diminish the residue deposits
Heavy bleeding & rough handling of the garment can cover up or dislodge some residues
GSR Distance Standards Made by firing the firearm,
using ammunition like that used in the actual case, into witness panels that consist of white pieces of cotton twill jean cloth
Several panels will be fired into at varying distances
GSR Distance Standards
Ballistic Gelatin Used by the shooting industry to simulate
soft body tissue Provides an alternative to live animal or
cadaver testing.
FUN! Go to
www.firearmsid.com Scroll over “Classroom” Click on Student Login Login Key:
C52840Forensics Full Name: Your’s &
Partner’s names Click on Cartridge Case
ID-VCM