BALLISTICS

The big picture of ballistics Because every contact leaves a trace (Locard’s exchange principle) very hard contacts (like a 180 mps to 1500 mps contact) will leave a big trace

History of Gunpowder and Firearms The Chinese invented gunpowder over a thousand years ago. Muzzle-loading matchlocks used wicks to ignite the gunpowder. The cartridge and breech loading followed. Rifling provided greater accuracy. Revolver, semi-automatic, and automatic handguns were developed.

Ballistics Ballistics – T he study of projectiles, trajectories, and the effect on the target Firearms Identification – A sub-discipline of ballistics that determining whether a bullet or cartridge was fired by a particular weapon

Introduction Ballistic evidence helps explain: What type of firearm was used. The caliber of the bullet. The number of bullets fired. Where the shooter was. Whether a weapon was fired recently. If a firearm was used in previous crimes.

AInternal ballistics What happens in the weapon BExternal ballistics What happens after the bullet leaves the barrel CTerminal ballistics (wound ballistics) What happens when the bullet hits the target

A Internal ballistics (1 of 3) INTERNAL BALLISTICS

SO WHAT’S A CARTRIDGE? a combination of: – a projectile (the bullet) – a propellant (gunpowder, for example) – a primer (the explosive cap), A

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

Watch this short video LsQ LsQ

How a gun Works 1. The firing pin hits the base of the cartridge, igniting the primer powder. 2. The primer powder sparks through the flash hole to the main propellant supply. 3. The pressure of the explosion pushes the bullet from the case into the barrel. 4. The bullet follows the lands and grooves spiraling out of the barrel.

Land = high Groove = Low BACK OF BULLET

A BROACH CUTTER USED TO CREATE RIFFLING IMPRESSIONS IN A BARREL

As a result of rifling, a barrel will impress a negative impression of itself on the sides of the bullet like those seen below. A

Matching impressions A

A fired bullet as class evidence Different gun manufacturers use different rifling techniques. These techniques impart the class characteristics on a fired bullet. – Number of impressions – Width of impressions – Depth of impressions – Angle of impressions

Q: How are these 2 guns different A: caliber

What is caliber? Caliber = the diameter of the bullet. Measured in hundredths of an inches. –.22,.357, or.50 Measured in metrics – 9mm Question: Why should the caliber of ammunition match the firearm that shoots it? If they do not match, what could go wrong? A

Showing variation within caliber

INTERNAL BALISTICS (2 OF 3) BREECH MARKS ARE FOUND ON THE REAR OF A FIRED CARTRIDGE A

A

Firing pin Breech

A

When a bullet is fired, the explosion forces: 1. the bullet down barrel 2. the cartridge back against breech – Leaving a negative impression on the back of the cartridge

Depending on the make of gun & normal wear and tear, the breech markings will pick up class, and hopefully, individual characteristics.

Examples of breech markings

How CSI determines if a recovered bullet from a crime scene came from a suspected gun qM qM Disclaimer: this video is oooooold

Shotguns have smooth barrels with no rifling. – Are there lands or groves on the bullet(s)? How can a F.S. identify trace evidence left by a shotgun? – Only by marks on the spent shell casing(s):

Shotgun into ballistics gel

B EXTERNAL BALLISTICS

External ballistics is everything that happens after the bullet leaves the gun to just before the BULLET impacts its target

GUN SHOT RESIDUE

GUN SHOT RESIDUE (GSR) CAN BE DETECTED EVEN AFTER WASHING CLOTHING / HANDS

Gunshot Residues Particles of unburned powder and traces of smoke are the residues of gunshots. They can leave a trace on: – Shooter hand, arm, face, hair, or clothing – Victim Chemical testing often can detect residue even if removal is attempted. The distance from the victim to the shooter can be determined by examination of the residue pattern on the victim.

Trajectory Path of bullet Horizon Wind shield Distance along path of bullet to window, 23.9” Distance along horizon to window, 23.5” y x 60 feet

Trajectory 2 Reference points needed to determine trajectory – can be bullet holes in objects or victims. Investigators can use lasers to trace a straight-line path to help determine the position of the shooter.

External ballistics

Point of initial intersection Maximum ordinate Point of secondary intersection Point of impact Point of aim

5 Ballistic Terms PII – Point of Initial Intersect. Where the bullet crosses the LOS (Line of Sight) for the first time. PII – Point of Initial Intersect. Where the bullet crosses the LOS (Line of Sight) for the first time. MO – Maximum Ordinate. The highest point the bullet reaches during its parabolic flight path. MO – Maximum Ordinate. The highest point the bullet reaches during its parabolic flight path. PSI – Point of Secondary Intersect. The point where the bullet crosses the LOS for the second time. PSI – Point of Secondary Intersect. The point where the bullet crosses the LOS for the second time. POI – Point of Impact. The point where the bullet impacts the target. POI – Point of Impact. The point where the bullet impacts the target. POA – Point of Aim. Where the shooter was aiming the weapon. POA – Point of Aim. Where the shooter was aiming the weapon. If the sights are properly adjusted: POI = POA = DOA (dead on arrival) POI = POA = DOA (dead on arrival)

C Terminal ballistics

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?

GUN SHOT RESIDUE

Bullet wounds (4 kinds) 1. Barrel on skin 2. Barrel just off skin 3. Barrel inches away 4. Shot from a distance

Notice: Distinctive star pattern, so… energy from the gun shot forced back out entryway “blowback” NO burnt gun powder marks around entryway, so… ALL gunpowder delivered inside entryway singing the interior (black area) Barrel on skin

Barrel inches away Notice: “stippling” of the burning powder around the actual bullet entry way No star pattern – No “blow back”

Barrel just off skin Notice: - no star pattern so.. – not ON skin No stippling from g.p. so.. – TOO close for inches away Barrel burns like on skin so…. – JUST off skin

Conclusion = shot from distance (probably through clothes) 9mm to person’s back NOTICE: – Lack of burnt gun powder burns on skin – Lack of star pattern

THE END

Shot from distance (but photo shopped)