Tennessee Bureau of InvestigationTennessee Bureau of InvestigationCrime LaboratoryCrime Laboratory

Firearms Identification UnitFirearms Identification Unit

Crime LaboratoryCrime Laboratory

Firearms Identification UnitFirearms Identification Unit

Firearms IdentificationFirearms Identification

• What Is Firearms Identification?

A di i li f F i S i hi hA discipline of Forensic Science which has as its primary concern to determine if b ll id hif a bullet, cartridge case, or other ammunition component was fired in a

i l fi h l i f llparticular firearm to the exclusion of all others.

Duties of TBI Firearm Identification UnitDuties of TBI Firearm Identification Unit

• Identification of fired bullets, cartridge cases, shotshell cases, and other ammunition components to their source.p

• Entry of fired cartridge cases into the IBIS Imaging System

• Toolmark Examinations

• Obliterated Serial Number Restoration

• Muzzle-to-Garment Distance Determination

• Crime Scene Technical Assistance• Crime Scene Technical Assistance

• Provide Expert Court Testimony as to the results of examinations.

• Bureau Armorer’s for all Bureau Issued Firearms

Requirements for the JobRequirements for the Job

• Must have a bachelor's degree from an accredited college or university in the natural or physical sciencescollege or university in the natural or physical sciences

• Must have a minimum of 24 semester hours in chemistryMust have a minimum of 24 semester hours in chemistry

• Must be comfortable around firearms

• Must pass a lie detector test

• Must undergo a psychological evaluation

• Must pass an extensive background check

Forensic Firearms LaboratoryForensic Firearms Laboratory

Bullet Class CharacteristicsBullet Class Characteristics

• How is Firearms Identification possible when dealing with fired bullets?

When firearms are manufactured, they receive what is known as “rifling.”

Rifling is a manufacturing process that cuts a series of lands and grooves into the barrel of the firearmlands and grooves into the barrel of the firearm.

The rifling is predetermined at the factory alsoThe rifling is predetermined at the factory, also known as “class characteristics”.

Rifling PatternRifling Pattern

Rifled Barrel CutawayRifled Barrel Cutaway

Bullet Individual CharacteristicsBullet Individual Characteristics

• When a bullet is fired through the barrel of a firearm:

The bullet expands into the lands and grooves

Th “ l h t i ti ” i d t th ftThe “class characteristics” are impressed onto the softer surface of the bullet.

i f i (i i i i i )The random imperfections (individual characteristics)present in the barrel are also transferred to the softer surface of the bullet.

The random imperfections are reproduced to form the “mechanical fingerprint” that makes that particular ec a ca ge p t t at a es t at pa t cu afirearm unique

Firearms ReferenceFirearms Reference Collection

Submitted Evidence Bullets/GunsSubmitted Evidence Bullets/Guns

The Firearms ReferenceThe Firearms ReferenceThe Firearms Reference The Firearms Reference CollectionCollection

Handguns, Rifles, Shotguns, Handguns, Rifles, Shotguns, Machine GunsMachine GunsMachine GunsMachine Guns

The Ammunition Reference The Ammunition Reference CollectionCollectionCollectionCollection

The Bullet Recovery TankThe Bullet Recovery Tank

Indoor Firing RangeIndoor Firing Range

Bullet ComparisonBullet Comparison

Cartridge Case ComparisonCartridge Case Comparison

Serial Number Serial Number RestorationRestoration

Remington 870Remington 870 BeforeBeforeRemington 870 Remington 870 -- BeforeBefore

Remington 870Remington 870 AfterAfterRemington 870 Remington 870 -- AfterAfter

MuzzleMuzzle--ToTo--MuzzleMuzzle ToToGarment DistanceGarment DistanceGarment Distance Garment Distance

DeterminationDeterminationDeterminationDetermination

Residues Exit BarrelResidues Exit Barrel

Lead Vaporous Cloud

Striations

Muzzle FlashMuzzle Flash

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