WARMUP How can impression evidence help us solve a crime? What are different types of impression evidence?

Assassination of JFK

FIREARMS UNIT 3

The Ten Commandments of Gun Safety

Random Fact!!! In 2004, there were 29,5769 gun deaths in the U.S. Suicides accounted for 56% Homicides were 40 %

In 1998, handguns killed…. 373 people in Germany 151 people in Canada 57 people in Australia 54 people in England and Wales 19 people in Japan

11, 789 People in the U.S. were killed with handguns in 1998

When did firearm production begin?? Gun powder invention in______ in the second century A.D. CHINA

TYPES OF FIRARMS

Handguns or Pistols Designed to be held in one hand Easy to _______ and conceal Not as accurate as other firearms Limited to the number of bullets they can hold Carry

2 Types of Handguns Revolver Cylinder that holds 6 bullets Has to be reloaded by hand AKA “SIX-SHOOTER” Semiautomatic Shoots one cartridge each time the trigger is pulled Reloads automatically Holds between 5 and 19 rounds

Revolver and Semiautomatic Semi-automatic Revolver

What is the difference between semi-automatic and fully automatic???? A fully automatic weapon keeps firing as long as the trigger is held back Machine gun is a good example of this

Rifles Longer barrel than handgun Butt stock that fits to the shoulder to steady the firearm and minimize kickback Shoot more powerful cartridges than handguns

Shotguns Similar to rifles, but used to shoot a packet of spherical pellets

Air Guns or BB Guns Shot or pellets are propelled by pressurized air, spring compression, or carbon dioxide cartridge

warmup Why is weapon identification a significant source of crime scene information?

DAY 2 AMMUNITION

© Precision Forensic Testing

Types of Ammunition Modern ammunition consists of Cartridge Case Primer Propellant Projectile

Bullet Type

Bullet Vocabulary Caliber- measure of the diameter Bore- inside diameter of the bullet Gauge- Size of a shotgun, related to the weight of the lead pellets Slug- Single pellet

Types of Bullets

Three Main Bullet Shapes

Types of Rifling Cut Rifling -

Types of Rifling Polygonal Rifling -

Class Characteristics All class characteristics are measurable Caliber Number of lands and grooves Width of the lands and grooves Direction of twist 123

Measuring the Class Characteristics Caliber Number of Lands/Grooves Direction of Twist Width of Lands/Grooves

Measuring Caliber Using a vernier caliper, measure the base of the bullet to the hundredths of a millimeter. This bullet measures millimeters Multiply millimeters by to determine inch measurement 11.5 x =.453 (approx..45 inches) Record your results 11.50

Types of Rifling Rifling is classified as being either “Cut” or “Polygonal” Polygonal (P) rifling has a smooth transition between lands and grooves Cut (C) rifling has defined shoulders Polygonal Rifling Cut Rifling

Counting the Lands and Grooves The grooves of the bullet are counted 1 23 It may be necessary to place a small mark with a felt tip pen in the location where counting begins.

Direction of Twist The twist is determined by sitting the bullet on a flat surface and observing the direction of the rifling. Left Right

Width of the Lands and Grooves Calipers are used to measure the width of the bullet lands and grooves

Weighing the bullet The bullet weight is recorded in grams Convert the weight from grams to grains 1 gram = grains

Bullet Type

Exercise #2: Determining the Possible Make of Firearm Based on Class Characteristics Using the measurements of the class characteristics, a list of possible makes of firearms can be established

Round Nose Maximum penetration

Hollow Point Least penetration Spreads on impact Causes additional damage to target

Hollow Point

Wad Cutter Used just for practice loads Creates a rip in paper that can be easily seen by shooter

Class Evidence Weight of bullet Dimensions of bullet Shape of bullet Type of bullet

Individual Evidence Striae- parallel sets of scratches on a bullet caused by unique markings in the bore of a rifled weapon Like a bar code Scratches on the cartridges caused by loading and unloading in the magazine

Give it a try! Fired Bullet Classifications!

DAY 3

What happens to bullets when they are fired? bsapp.co m

Pull the Trigger and... 1.A pin or hammer strikes the primer. This causes a spark. 2.The powder is then ignited causing an explosion. 3.This explosion starts the bullet down the barrel of the gun bsapp.co m

Down the Barrel 1.As a bullet travels down the barrel of a gun it is twisted by the lands and groves of the barrel. bsapp.co m

Out of the Barrel 5.This rifling causes the bullet to exit the end of the barrel in a spiral motion. bsapp.co m

What happens to a bullet when it hits a target?  Most bullets tend to mushroom when they hit a target.  Some bullets nearly disintegrate.  Left are bullet fragments from a ½ jacketed hollow point. bsapp.co m

Not all bullets mushroom the same. A lot depends on the speed and shape of the bullet, and the characteristics of the target. bsapp.co m

Some more bullets recovered after firing The striations from the rifling are still visible bsapp.co m

Distance From Target Important to know distance from muzzle to target in order to reconstruct the event As bullet leaves muzzle, it carries some of the unburned particles along with as well as the combustion products

Greiss Test Nitrites are primary combustion product The Greiss Test can chemically convert nitrite to colored products

Gunshot Residue Burned and unburned powder, vaporized and particulate lead, primer residues of lead, barium, and antimony GSR can be found on the shooter’s hand

How does manufacturing characteristics of guns aid in the identification of specific weapon and possible perpetrator?

Forensic ballisticsballistics is the application of ballistics (characterizing firearms) to address legal questions.

Ballistic fingerprinting refers to a set of forensic techniques that rely on marks that firearms leave on bullets to match a bullet to the gun it was fired with. forensicfirearms bullets

Firing Mechanism (semiautonmatic, single action…etc.) Ammunition Traits ( head stamp, shape, profile….etc.) Bullet type (boat tail, wadcutter…..etc.) Firearm Barrel characteristics (rifling, lands and grooves….etc.)

Trigger is pulled! The hammer withdraws and rapidly strikes the back of the bullet. The shock of the strike causes an explosion of the primer. The gunpowder combusts. This propels the bullet or slug.

Most primer blends contain: Lead, antimony and barium. Other components can be used. Gun powder: Main ingredient cellulose nitrate These materials causes and exothermic reaction and where heat escapes so too does unused material.

Your task: Test +/- and yourself! SR D