Firearms and Tool Marks Flashcards
Shot Gun
has a long, thin, smooth barrel
Land
part of a bullet or bore that is raised
gunshot residue
gases, soot, unburned or partially burned gunpowder released when a shot is fired
tool mark
any cut, scrape, impression, gouge, scratch, indentation or other mark left on an object or surface at a crime scene
semi-autmatic
gun that fires a single round with a trigger pull and reloads itself
caliber
the diameter of the bore or bullet
shot
numerous round metal pellets
smokeless
is the most common type of gunpowder used in ammunition today
gunpowder
highly flammable material that pushes the projectile out of the gun barrel
handgun
has a short, rifled barrel
made up of a case, primer, powder, and bullet
cartridge
microscopic markings left on the surface of a bullet
striations
made up of a casing, shot, wad, powder and primer
shell
groove
part of a bullet or bore that is pressed in
spiral grooves impressed into the barrel of a firearm
rifling
rifles
has a long, thick rifled barrel
primer
substance that ignites the gunpowder after being struck by the firing pin
crime lab firearm identification units provide knowledge on
operation of all types of weapons
recognition, of different types of ammunition
detection and characterization of gunpowder residue
polygonal rifling
land and groove edges look rounded, older
the trigger is pulled, causing the firing pin to strike the primer, then
the primer ignites the gunpowder inside the cartridge and the burning gunpowder produces gases which create pressure to propel the bullet through the barrel
caliber
diameter
to measure the land and groove characteristics you look at the
width, number, and twist
breechface striations are
results from contact with the rear wall of the firing chamber
firing impresssions
marked upon primer when the cartridge is stuck, shape is indented in the primer, rim of cartridge case
extractor markings
usually found in a striated form, a hook that is used to remove a cartridge or cartridge case from the chamber of a firearm.
ejector marks
shape impressed on the head stamp of cartridge case when pushed
National integrated ballistic information network (NIBW)
database of digital microscopic images of spent bullets and cartridge casings from crime scenes or test fired
Contact point black
muzzle of gun is touching victims skin or clothing, visible around bullet hole, tears in fabric, skin
close range
less than 6 inches, GSR can be embedded around bullet hole, pattern small and dense, pattern increases w distance
medium range
gun is 1.5-3 ft from target
long distance
greater than 5 ft
compression indentation
produced by pressing an object against softer surface
sliding/ abrasion
when surfaces slide
scratches and striations
cutting marks
along edge of surface as it is cut
bullet wipe
The discolored area on the immediate edge of a bullet hole, caused by bullet lubricant, lead, smoke, bore debris, or possibly jacket material.
