Ballistics

Projectiles

Definition: any material that travels with the ability to injure

Energy is dependent on the velocity, mass, and distance traveled by projectile

Not all projectiles come from fire arms!!!

Projectile

Formula: KE = mv2

2 Velocity usually plays the major role in

the kinetic energy Over whelming weight (mass ) can

makeup for a slow velocity (Hit by a car)

Shape of a projectile will determine how well an object can slice through atmosphere and hence how well it will maintain velocity

Kinetic Energy

Fire Arms

Definition: A discipline mainly concerned with

determining whether a bullet or cartridge was fired by a particular weapon

Fire Arms Identification

1st: Always assume that the fire arm is loaded◦Do NOT assume gun is safe until it is

processed evidence 2nd: Pick up carefully at grip and make sure to

keep fire arm pointed to the ground or up away from anyone.◦Grip of a gun is hard to find or collect

evidence from therefore you maintain integrity of physical evidence

3rd: Never poke or put anything in the barrel it may destroy evidence. To make the gun safe remove ammunition.

4th: Take note of amount of ammunition remaining in chamber and cartridge along with number of ammunition missing.

5th: Have the gun confirmed by a second professional that all ammunition has been removed

Collection of Fire Arm Evidence

Landmarks

A

A

BB

B

Barrel Contains: A) LandB) Grooves

Bullet Contains:A) Land ImpressionsB) Groove Impressions

Rifling: the spiral grooves that are formed in the bore of a fire arm barrel, which makes the projectile spin when firedCaliber: diameter of the bore of a rifled fire arm which is measured from one land to another land (measured in mm or hundredths of an inch)

Cartridge Parts and How it Works

Primer

Cartridge Casing Gun Powder

Lead Bullet

Bullet Comparison Class Characteristics

◦ Number of lands and grooves

◦ Width of lands and grooves

◦ Depth of lands and grooves

◦ Twist◦ Cartridge Case

(manufacturer, shape, caliber, composition)

Individual Characteristics◦ Machine markings◦ Striations◦ Impressions◦ Firing Pin Impressions◦ Extractor and Ejector

Marks

Class Characteristics

Different gun manufacturers use different rifling techniques which are shown in the class characteristics of the bullet

Number of lands and grooves

Width of lands and grooves

Depth of lands and grooves

Twist (Left or Right)

Cartridge Case Class Characteristics

Manufacture ( i.e.. Winchester)

Shape ( i.e.. rimless, rimmed )

Caliber ( i.e.. 45 ACP, 9mm, 12 gauge)

Composition ( i.e.. brass, steel, plastic)

Bullet Individual Characteristics

Machine markings: a cross section of a gun barrel that shows groove or striations along the lands and grooves of the bullets

These are created when a barrel is rifled. No two guns have the exact same rifling

It is possible to match multiple bullets to the same gun using the striations left on the bullet

Matching Striations

A

B

Cartridge Case Individual Characteristics

Firing Pin Marks: To fire the cartridge the primer must be ignited. This is accomplished by the firing pin hitting the center ring of the cartridge which is unique to every gun

Cartridge Case Individual Characteristics (Cont’d)

Extractor and Ejector Marks: The extracting pin and ejector throw the spent casing from the chamber of the gun which leave individual characteristics on the shell casing that can be used for identification of the gun which fired that casing

Gun Parts where Individual Characteristics are created

Firing Pin

Extracting PinBreech

Shot Gun Exception Shotguns have smooth barrels with not

rifling. Therefore there are no land or groove marks left on the bullet. Identification can still be made by comparison of extractor/ ejector markings on shotgun shell.