ballistics bullets and casings. t imeline of b allistics e xamination 1923: fbi bureau of forensic...
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BALLISTICSBullets and Casings
TIMELINE OF BALLISTICS EXAMINATION
1923: FBI Bureau of Forensic Ballistics established
1929: weapons used in the St. Valentine’s Day massacre identified by matching bullets
1992: Drugfire database is established 1996: NIBIS is established by the ATF 2000: NIBIN is established by merging of
Drugfire and NIBIS
TYPES OF BULLETS
Full Metal Jacket: projectile in which the bullet jacket encloses the entire bullet, with the usual exception of the base; most common use of this ammunition is target shooting
TYPES OF BULLETS (CONT.)
Jacketed Soft Point: bullet designed with the soft lead core exposed at the nose; typically used for hunting; usually have Cannelure--groove around a bullet or cartridge case; Typically found on revolver and rifle bullets
TYPES OF BULLETS (CONT.)
Jacketed Hollow Point: bullet designed with a jacket, typically copper, surrounding the lower portion; the nose of the bullet has a hollow point; allow for easier expansion or “mushrooming” upon contact with an object; this increases the surface area of the bullet
TYPES OF BULLETS (CONT.)
Lead Round Nose: elongated projectile made of a lead alloy with a rounded nose; typically used for target shooting
TYPES OF BULLETS (CONT.)
Semi-wadcutter: bullet designed with a truncated nose and sharp shoulder; used for target shooting, the sharp shoulder on the bullet produces a clean round hole in paper
TYPES OF BULLETS (CONT.)
Wadcutter: cylindrical bullet with a sharp shouldered nose intended to cut target paper cleanly to facilitate easy and accurate scoring
TYPES OF BULLETS (CONT.)
Boat Tail: bullet having a tapered or a truncated conical base; the tapered cone provides increased stability throughout it’s flight
TEST-FIRE
Weapon is fired into a water tank or gel block This captures the bullet without damaging it The test-fire bullet can be compared to
markings on the suspect bullets
CLASS CHARACTERISTICS All class characteristics
are measurableCaliberNumber of lands and
groovesWidth of the lands and
groovesDirection of twist
1 2 3
MARKS ON CARTRIDGES
Firing Pin Marks: made on the bottom of the cartridge by the firing
pin as it strikes the bottom of the cartridge when the firearm is shot
usually appears on the center of the cartridge
MARKS ON CARTRIDGES (CONT.)
Breechblock Marks: during the shot, the explosive force pushes the
bullet forward and at the same time, an equal and opposite force pushes the cartridge casing backward against the breechblock, leaving marks on the casing
the breechblock prevents the cartridge from shooting toward the user as it recoils
marks appear as parallel lines, circular lines, or stippled pattern
MARKS ON CARTRIDGES (CONT.)
Firing Pin Mark Green arrows are pointing to parallel breechblock marks
MARKS ON CARTRIDGES (CONT.)
Extractor and Ejector Marks: Minute scratches produced as the cartridge is
placed in the firing chamber are extractor marks
Scratches produced as the cartridge is removed from the chamber after firing are ejector marks
Extractor and ejector marks are produced only in semi- and fully automatic weapons
DATABASES
National Integrated Bullet Identification System (NIBIS): ATF database that has computer files of ballistic markings of firearms used in previous crimes
Drugfire: FBI database that focuses on cartridge casings
These two databases were merged to form the National Integrated Ballistics Information Network (NIBIN)