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
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
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
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
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
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