firearms 2

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.