Ballistics and Firearms Ballistics- Study of a projectile in motion Firearm Identification- Study of whether a bullet or cartridge case was fired from a weapon

Firearms 3 categories Handgun Rifle Shotgun

Firearms 3 categories: Handguns Revolvers vs. semi-automatics Revolvers- Rotating cylinder holds the bullets. Consists of 6 individual spaces. Semi-automatics- Loaded using a magazine/clip. Holds 6-15 rounds

Semi-Automatic The Revolver

Firearms Rifles Shotguns Gun with a long rifled barrel Used for long distance targets Shotguns Gun that fires cartridge cases with pellets Pellets are a.k.a shot Not a precision weapon because pellets spread out in a circular pattern Barrels are smooth not rifled and are wider than other gun barrels

Shotgun Rifle

Vocabulary Rifling- Technique of forming grooves in the bore of a barrel to give spin to the bullet Bore- Interior of barrel Lands- Raised portion between grooves in bore Grooves- Cut portions in bore

Figure 15–1  Interior view of a gun barrel, showing the presence of lands and grooves.

Cross-section of a barrel with six grooves Cross-section of a barrel with six grooves. The diameter of the bore is the caliber.

Rifling Techniques Broach Cutting- Steel rings cut into the barrel forming a spiral bore Button Technique- Steel button is forced under high pressure into the barrel Mandrel Technique- Rod of steel with a shape that’s the reverse of the intended impression is placed in an oversize bore and then it is compressed.

Class Characteristics Characteristics of a class/group of weapons Number of lands Number of grooves Width of lands and grooves Direction of twist Rifling technique

Individual characteristics Specific striations that are found on recovered bullets and cartridge casings Each weapon has a unique bore Firing pin leaves striations/impressions Breech Block leaves striations/impressions Ejector and Extractor leave striations/impressions

The Comparison Microscope Both the evidence bullet and the test bullet are examined at the same time in the same field of view One bullet is rotated until a well-defined land or groove is found

Caliber vs. Gauge Caliber- Measurement of the diameter of the bore. Expressed in hundredths of an inch or mm .35 Caliber or 9mm Gauge- Measurement or size designation of a shotgun. Number of lead balls that fit inside a shotgun barrel (equal to the interior diameter of barrel) Shotgun barrels are smooth not rifled As Gauge increases, barrel diameter decreases

*The systems could not work together. Databases IBIS (Integrated Ballistic Identification System) – Database developed for the Bureau of Alcohol, Tobacco, Firearms and Explosives branch of the government. DRUGFIRE – Automated search system developed for the FBI. *The systems could not work together. NIBIN (National Integrated Ballistic Information Network) – Was created to integrate IBIS & DRUGFIRE

Entry Wounds and Muzzle Distance of handgun or rifle If the muzzle is 2 or more ft. away from the victim the entrance wound is a small hole w/ a bruise called an abrasion collar surrounding it.

2. If the muzzle is between 6 in. and 2ft 2. If the muzzle is between 6 in. and 2ft. The wound appears “tattooed” from the gun powder Known as stippling

3. If the muzzle is less than 6 in 3. If the muzzle is less than 6 in. from the victim the wound has a compact area of stippling, surrounded by bright red tissue.

4. If the gun is fired at “point blank” range hot gases and gun powder are driven directly into the skin .The skin is scarred into a star shaped pattern.

Additional Info

Collection & Preservation of Evidence Firearms: Unload weapon and record the position of hammer and safety Record the location of all fired and unfired ammunition in weapon Mark chamber position on a revolver. For automatic weapons, remove magazine check for prints Place each round in a separate envelope Label firearm with tag attached to trigger guard. Include serial number, make , model, and your initials

Ammunition Free bullets from target by carefully breaking away surrounding material- avoid direct contact with bullet Bullets are individually wrapped in tissue and placed in envelope

EXAMPLE NOTES Chamber Position/ Condition Cartridge/ Headstamp ---------------------- --------------- --------------------------- 1 Fired U.S.C. Co. 2 Fired REM-UMC 3 Fired WRA 4 Misfired D.C. Co. 5 Loaded WESTERN 6 Loaded PETERS

The Basics of Firearms Step 1: The bullet enters the firing chamber. Step 2: The hammer is drawn back. Step 3: The trigger is pulled throwing the hammer forward. Step 4: The hammer or firing pin strikes the primer igniting the gun powder. Step 5: The gases released from the exploding gun powder drive the bullet down the gun barrel. Step 6: The breechblock absorbs the recoil and holds the casing in place. Step 7: The casing is then removed from the chamber by the extractor. Step 8: The casing is then thrown from the gun by the ejector.