Ballistics: Introduction Ballistics: Introduction

Ballistic evidence helps explain:

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Long Guns and Handguns• Long guns

• Handguns

• Automatic and Semi-automatic

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Firearms and Rifling Firearms and Rifling

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Bullets, Cartridges, and Bullets, Cartridges, and Calibers Calibers

• Cartridge—

• Semi has 10 cartridges in a magazine (clip)

• The bullet, usually of metal, is out front with the cartridge, holding the primer and propellant powders, behind.

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How a Firearm Works How a Firearm Works

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How a Firearm Works How a Firearm Works

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Caliber of the Cartridge Caliber of the Cartridge

• Caliber—a measure of the diameter of the cartridge (stamped on headstamp on the bottom of the cartridge casing)

• In hundredths of an inch• Common calibers include

.22, .25, .357, .38, .44, and .45

• Why should the caliber of ammunition match the firearm that shoots it? If they do not match, what could go wrong?

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The Study of BulletsThe Study of Bullets and Cartridge Casings and Cartridge Casings

1. How is each fired bullet marked? 2. What is the procedure to match a spent bullet to the

firearm that shot it? 3. What makes up a test-firing, and why is it done?

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Marks on the Marks on the Spent Cartridge Casings Spent Cartridge Casings • Firing pin marks

• Breechblock marks

• Extractor marks • Ejector marks

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Gunshot Residues Gunshot Residues • Gunshot Residues (GSR)

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Trajectory Trajectory • Two reference points are needed to define the

trajectory • Investigators can

figure the shooter discharged the firearm somewhere along that line

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Trajectory Trajectory

• Reference points can be • bullet holes in objects or victims• An entry point and exit point on a victim • Gunshot residue or spent cartridge casings

• Lasers can trace a straight-line path to determine the position of the shooter

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Determining the Location of the Shooter Building is 60 feet away along the horizon lineBullet hole is 4 feet above the ground

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Where is the shooter located?

Triangulation

• B is where the shooter is located; find the length of BC• The Abc triangle has the same proportions as the ABC

triangle

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Triangulation

• Using Pythagorean’s theorem AB2 = AC2 + BC2

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Bullet Wounds Bullet Wounds 1. Why do entrance wounds tend to be smaller than exit

wounds? 2. If the bullet penetrates clothing, what can fibers embedded

in the wound indicate? 3. Where is gunshot residue usually found? 4. If the gun is fired with the muzzle touching the victim’s

skin, what telltale mark may show up? 5. Will larger or will smaller caliber bullets tend to lodge

within the body rather than passing through? Why?

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16Kennedy assassination recreationhttp://www.youtube.com/watch?v=R5JDhi4URds