Projectiles Definition any material that travels with the ability to injure Energy is dependent on the velocity mass and distance traveled by projectile Not all projectiles come from fire arms ID: 300056
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Slide1
BallisticsSlide2
ProjectilesSlide3
Definition: any material that travels with the ability to injure
Energy is dependent on the velocity, mass, and distance traveled by projectile
Not all projectiles come from fire arms!!!
ProjectileSlide4
Formula:
KE =
mv
2
2Velocity usually plays the major role in the kinetic energy
Over whelming weight (mass ) can makeup for a slow velocity (Hit by a car)
Shape of a projectile will determine how well an object can slice through atmosphere and hence how well it will maintain velocity
Kinetic EnergySlide5
Fire ArmsSlide6
Definition: A discipline mainly concerned with
determining whether a bullet or cartridge was fired by a particular weapon
Fire Arms IdentificationSlide7
1
st
: Always assume that the fire arm is loaded
Do
NOT
assume gun is safe until it is processed evidence
2nd: Pick up carefully at grip and make sure to keep fire arm pointed to the ground or up away from anyone.
Grip of a gun is hard to find or collect evidence from therefore you maintain integrity of physical evidence
3
rd
: Never poke or put anything in the barrel it may destroy evidence. To make the gun safe remove ammunition.
4
th: Take note of amount of ammunition remaining in chamber and cartridge along with number of ammunition missing. 5th: Have the gun confirmed by a second professional that all ammunition has been removed
Collection of Fire Arm EvidenceSlide8
Landmarks
A
A
B
B
B
Barrel Contains:
A) Land
B) Grooves
Bullet Contains:
A) Land Impressions
B) Groove Impressions
Rifling
: the spiral grooves that are formed in the bore of a fire arm barrel, which makes the projectile spin when fired
Caliber
: diameter of the bore of a rifled fire arm which is measured from one land to another land (measured in mm or hundredths of an inch)Slide9
Cartridge Parts and How it Works
Primer
Cartridge Casing
Gun Powder
Lead BulletSlide10
Bullet Comparison
Class Characteristics
Number of lands and grooves
Width of lands and grooves
Depth of lands and grooves
Twist
Cartridge Case (manufacturer, shape, caliber, composition)
Individual Characteristics
Machine markings
Striations
Impressions
Firing Pin Impressions
Extractor and Ejector MarksSlide11
Class Characteristics
Different gun manufacturers use different rifling techniques which are shown in the class characteristics of the bullet
Number of lands and grooves
Width of lands and grooves
Depth of lands and grooves
Twist (Left or Right)Slide12
Cartridge Case Class Characteristics
Manufacture ( i.e.. Winchester)
Shape ( i.e.. rimless, rimmed )
Caliber ( i.e.. 45 ACP, 9mm, 12 gauge)
Composition ( i.e.. brass, steel, plastic)Slide13
Bullet Individual Characteristics
Machine markings
: a cross section of a gun barrel that shows groove or striations along the lands and grooves of the bullets
These are created when a barrel is rifled. No two guns have the exact same rifling
It is possible to match multiple bullets to the same gun using the striations left on the bulletSlide14
Matching Striations
A
BSlide15
Cartridge Case Individual Characteristics
Firing Pin Marks
: To fire the cartridge the primer must be ignited. This is accomplished by the firing pin hitting the center ring of the cartridge which is unique to every gunSlide16
Cartridge Case Individual Characteristics (Cont’d)
Extractor and Ejector Marks
: The extracting pin and ejector throw the spent casing from the chamber of the gun which leave individual characteristics on the shell casing that can be used for identification of the gun which fired that casingSlide17
Gun Parts where Individual Characteristics are created
Firing Pin
Extracting Pin
BreechSlide18
Shot Gun Exception
Shotguns have smooth barrels with not rifling. Therefore there are no land or groove marks left on the bullet. Identification can still be made by comparison of extractor/ ejector markings on shotgun shell.