Firearms and Ballistics

Firearm Examination

examination and identification of the firearm and ammunition.

• type of firearm used

• caliber of the bullet

• does the crime scene bullet match the suspects gun

• was the firearm involved in previous crimes

Ballistics

examination and comparison of projectiles in motion.

• where the shooter was standing

• shooting distance from the victim

9th Century

black powder was invented

1465

muskets first appear in the Ottoman Empire

Rifled Barrel

• handguns

• rifles

Smoothbore Barrel

• shotgun

• antique black powder weapons

Caliber

Caliber is a measure of the diameter of the cartridge.

Measure from tops of two opposing lands.

Usually measured in hundredths of an inch

Common caliber include .22, .25, .357, .38, .44, .45

Pistols

• semi-automatic and automatic

• spring loaded magazine

• casings are ejected after each firing

Revolver

• manual

• revolving cylinder

• casings are contained within the cylinder until removed

Rifles

• designed to be used with two hands from the should

• single shot, slide action

• semi-automatic

• automatic

Automatic

continually fires until trigger is released

Semi-automatic

fires each time the trigger is pulled

Smoothbore Firearms

No rifling present.

Since there are no rifling marks, its much harder to match a shotgun pellet to a specific firearm.

Instead investigators analyze pellet spread, wadding patterns, and gauge

Shotguns

Designed to be fired with 2 hands from the shoulder.

Can fire slugs or shots

• slug: single projectile with modifications

• shot: pellet loads that spread after being fired

Cartridges

• different types come from different weapons

• usually stamped with maker

• rimmed, rimless, semi rimmed, belted, rebated

Serial Numbers

criminals tend to try and remove the serial number.

can be recovered by chemical etching.

This is the only real individual characteristic of firearms.

Class Characteristics bullets

• caliber

• direction of twist

• degree of twist

• number of lands and grooves

• width of lands and grooves

Individual Characteristics bullets

• striation marks

• skid marks

• shaving marks

Skid Marks

caused by the bullet sliding over the beginning of the lands.

towards the tip of the bullet

Shaving Marks

occurs when revolver bullet does not line up with the barrel.

some of the bullet gets shaved off

Cartridge Examination Class Characteristics

• size

• shape

• type

• size of firing pin impression

• position of firing pin impression

Cartridge Examination individual characteristics

• location of extractor marks

• location of ejector marks

• accidental marks