firearms 2
DESCRIPTION
TRANSCRIPT
Firearms – part 2
Bullet Holes The bullet holes are smaller in diameter than
the bullet due to the elasticity of the fabric
Higher the velocity = the greater the damage
Bullet wipe residue – traces of lead leave a ring of residue
GSR
When gases combust Propel bullet Blow out from ejector
port and muzzle
GSR Ejector particles Combustion
residue Unburned powder
particles
GSR – travel 3 – 5 feet
As firearm gets closer – the residue concentrations increase
Elements contained in GSR are not water soluble therefore the residue will remain on clothing
GSR ExaminationsVisual/Microscopic Examination
Greiss Test
Sodium Rhodizonate
Greiss Test Performed 1st does not interfere with later tests
Detects nitrites (product of combustion)
Used to determine muzzle to garment distance
Steps of Greiss Test
Treat photographic paper with chemical mixture – paper will no longer be light sensitive but will be reactive to the presence of nitrite residues
Particle being processed placed faced down against treated photo paper – bullet hole centered
Steam ironed - dilute acetic acid
Steps continued Acetic acid will react with nitrites and
chemicals in photographic paper
Resulting in orange specks
Using same firearm – make test samples from various distances
Determine Minimum firing distance (the gun could be no
closer than) Maximum firing distance (the gun could be not
any further than
Greiss Test – 3 inches
Greiss Test – 9 inches
Greiss Test – 15 inches
Greiss Test – 21 inches
Sodium Rhodizonate Test
Determines if lead residues are present
Spray particle with sodium rhodizonate solution (dark yellowish/orange color)
Sprayed with buffer solution – causes background color to disappear
Sodium Rhodizonate Test
Sodium rhodizonate reacts with lead – very bright pink
Pink – only indication of presence of lead
To confirm – area treated with Hydrochloric acid
If pink turns blue – presence of lead confirmed
GSR results - 3 categoriesResidue, firearm and ammunition found
Residue found – firearm and ammunition not found
Trace or no residue found
Gunshot wounds are typically classified as Contact Intermediate range Distant range
Contactbarrel
contacts the skin
the gases released cause the star-shaped laceration.
Contact The abrasion
ring, and a very clear muzzle imprint, are seen in this contact range gunshot wound.
intermediatePowder tattooing
The actual entrance site is somewhat irregular, because the bullet can tumble in flight.