Ballistics

What is Forensic Ballistics

Ballistics: The Science of the mechanics that deals with motion, behavior, and effects of projectiles

Forensic Ballistics: Science of analyzing firearm and weapon usage in crimes Firearm Identification Firearm components Ammunition/Ammunition components Toolmark analysis

What are Projectiles?

Projectiles: An object propelled through space an exertion of force that ceases after launch Bullets, gravity bombs,

rockets, scrape metal

Kurt Cobain (2/20/67 – 4/5/94)

What is a Ballistic Body?

Ballistic Bodies are those that are free to move, behave, and be altered or modified in appearance and contour by ambient conditions, substances, and forces. Ambient = surrounding Contour = path Example: Pitching a baseball

Ballistic History

9th century A.D. - Chinese discover gun powder Potassium Nitrate (KNO3), charcoal, sulfur Expands to 6 times its size when heated Fireworks and cannonballs

14th century A.D. – Europe Matchlock guns

Contained a barrel and wick on a piece of wood 18th century A.D. – Europe

Cartridges: case that holds a bullet, primer powder, and gun powder

Bullet: pointy projectile that is released when a firearm is discharged

Samuel L. Colt

1835: Colt creates the first firearm that can be shot multiple times without reloading

Ballistic History In Court

1902: 1st court case involving firearms evidence

Oliver Wendell Holmes proved

murder weapon by test shooting

Alphonse Gabriel Capone a.k.a.“Scarface” & the St. Valentines Day Massacre

Ballistic History cont… Calvin Goddard

Pioneer for Firearms Identification Acquired data from all well-known gun manufacturers Established database Comparison Microscopes to compare and contrast test fires

Coined term “Forensic Ballistics” Established the Bureau of Forensic Ballistics in NYC

1929: St Valentines Day Massacre Event led to the opening of ballistic crime detection

laboratory

Ballistic History cont…

1930: Earliest gunshot residue (GSR) test is performed  It is principally composed of burnt and unburnt

particles from the explosive powder – and possibly the components of the bullet, cartridge case, and firearm

1968: 1st use of scanning microscope for comparing GSR.

History cont…

1992: FBI established Drugfire database Compiles details on bullet and cartridge

markings 1996: U.S. Bureau of Alcohol, Firearms,

and Tobacco (AFT) establish database for spent ammunition

2000: FBI and AFT begin merging databases

Types of Guns

1. Long guns Shot guns and

rifles Rifles bullets Shot guns Small

round pellets (shot) or a single projectile (slug)

Require 2 hands for accurate firing

Types of Guns

2. Handguns One hand to operate Pistols single bullet Revolvers

Cylinder that holds the cartridges turns as gun is fired, allows for several cartridges to be fired in rapid succession

Holds 6 cartridges

Automatic Weapons

Semiautomatic Holds up to 10 cartridges into a magazine (clip) 1 bullet fired per pull of the trigger

Automatic Weapons

Fully Automatic Multiple rounds are fired when the trigger

is held down

Anatomy of a Cartridge

Bullet: Projectile that is

extracted from the cartridge

Usually lead or copper

Metal-jacketed, hollow-pointed, or plastic

Anatomy of a Cartridge cont…

Primer powder Struck by firing pin Pressure causes

ignition Flash hole

Delivers the explosive charge from primer powder to gun powder

Anatomy of a Cartridge cont…

Headstamp Bottom of the

cartridge casing

Caliber and Manufacturer info

Gun Ballistics

From the time of shooting to the impact upon a target

Broken down into 4 different branches1. Internal Ballistics

2. Transition Ballistics

3. External Ballistics

4. Terminal Ballistics

Internal Ballistics

Def: The study of the processes that originally accelerate the bullet Example: The passage of a bullet

through the barrel of a rifle

Rifling (Internal Ballistics)

Rifling are helical (spiral) grooves that are cut into a bore of a firearm

1. Bore: Interior of a firearm

2. Lands: Raised portion of rifling.

3. Grooves: Indented portion of rifling

4. Caliber: Diameter of the bore– Usually expressed hundredths of an inch or

mm

Why Significant? (Rifling)

1. No 2 rifled barrels are the same• Even those manufactured by the same

company• Lands and Grooves leave marks on the

bullet• As unique as fingerprints

• Wear and tear from machine

makes each gun unique

Why Significant cont…

2. Increase Accuracy• Lands and grooves cause bullet to spin

3. Increase Speed• The faster a bullet spins the easier it cuts

through the air, thus allowing it to travel faster

Transition Ballistics

Def: Study of the projectiles behavior once it leaves the barrel and the pressure behind the projectile is equalized

This accounts for the loud sound a gun makes when fired

External Ballistics

Def: Study of the projectile through air and space

There are two main forces that act upon the projectile

1. Gravity: drops the bullet

2. Air resistance: decelerates the bullet

Bullet Movement (Ext. Ballistics)

Bullet Drop 3 feet over a distance of 500 yards

Bullet Rise Bullet rises before it drops

Due to force from being fired Rise can be up to about 14 inches

Bullet Drop and Bullet Rise

JFK Autopsy Pictures

Factors that would affect Bullet Movements

1. Gun Type2. Bullet Weight3. Weather conditions

How about for extremely long ranges (missiles)?

4. Coriolis Effect Deflection of an object due to the rotation of the

Earth

Terminal Ballistics

Def: Study of the interaction of the projectile with its target Also referred to the stopping

power when dealing with human or living tissue

Only relevant for smaller projectiles

3 Classes of Bullets

Terminal Ballistics depends on the class of bullet

1. Maximum Accuracy

2. Maximum Damage w/Total Penetration

3. Maximum Damage w/Controlled Penetration

Total Penetration Bullets

Want to focus the most momentum on the smallest possible target

Armored targets/Large game animals Tips are…

Sharp Lead covered in metal coat

Resist Deformation

Controlled Penetration Bullets Designed to inflict maximum

damage on a living target Designed to increase surface

area upon impact1. Expanding Bullets (Hollow

Tip) Sharp tips with nothing behind

them Covering opens up upon impact

Larger Hole Slows Impact

“Mushroom” effect

2. Fragmenting Bullets Designed to break apart upon impact Differ from that of hollow points in that they do

NOT stay in one piece Used for small game

3. Frangible Bullets Similar to Fragmenting…break apart upon

impact Differ: NOT hollow Hostage Situations

Gun Shot Residue (GSR)

GSR = residues of smoke and particles of unburned powder carried sideways from the firearm by the expansion of gases as the bullet is fired.

Stick to shooter

Gun Shot Residue

Residue can travel out of the gun from distances of 3-5 feet Sticks to both shooter and victim Amount of GSR decreases as the

distance between firearm and victim increases Helps to determine distance between shooter

and victim