FIREARM-IDENTIFICATIONS (1)

Firearm Identification

1. Definition of Firearms Identification

  • Refers to the science of determining if a bullet was fired from a specific gun.

  • Reveals pertinent facts about firearms or ammunition.

2. Marks Found on Fired Bullets

  • Land Marks

    • Depressed portions caused by the lands of the barrel.

  • Groove Marks

    • Elevated portions caused by the grooves in the barrel.

  • Slippage Marks

    • Result from worn-out, oily, or oversized barrels.

  • Shaving Marks

    • Marks from revolvers due to misalignment of the cylinder and bore.

  • Striations Marks

    • Common in cartridge cases from auto-loading or repeating firearms:

      • Chamber Marks

      • Shear Marks

      • Extractor Marks

      • Ejector Marks

3. Principles of Identification of Fired Bullets

  1. No two barrels are microscopically identical.

  2. A bullet fired from a rifled barrel is engraved, leading to unique markings.

  3. Each barrel leaves a unique “thumb mark” on every bullet fired through it.

4. Marks Found on Fired Shells

  • Firing Pin Impression

    • Indentations from the firing pin striking the cartridge’s primer or rim.

  • Breech Face Mark

    • Marks found at the head of the cartridge case, characterized by:

      • Heavy left side

      • Vertical

      • Sandblasted

      • Mottled

      • Rim dents

      • Mouse ears

  • Extractor Mark

    • Striated marks from the extractor of auto-loading/repeating firearms.

  • Ejector Marks

    • Marks from cartridges ejected from the firearm.

  • Shearing Marks

    • Secondary firing pin marks, found near the firing pin mark.

  • Chamber Marks

    • Striated marks caused by roughness in the firearm's chamber.

  • Magazine Lip Mark

    • Marks produced by the magazine lip on the cartridge case.

5. Principles of Identification (Fired Shells)

  1. Individual characteristics exist on the breech face and striker of each firearm.

  2. Each fired cartridge is imprinted with the firearm’s unique fingerprint.

6. Recovering and Preserving Evidence

  1. Handle items carefully to avoid alteration or damage.

  2. Do not process firearms evidence for prints before laboratory examination.

7. Marking of Firearms Evidence

  1. Initials, time, and date on each item of evidence.

  2. Use marking tools for inscribing unique markings on firearms evidence.

  3. Mark multiple places on the firearm for identification.

8. Transmittal of Evidence

  1. Use appropriate containers for evidence:

    • Pillboxes, plastic vials with cotton packing.

    • Seal with paper tape; avoid cellophane/masking tape.

  2. Create diagrams of loaded or fired cartridges in revolvers for lab examiners.

9. Testing at the Lab

  • Lab can identify class characteristics of the firearm involved, such as:

    • Caliber

    • Type of firearm (revolver, pistol, rifle)

    • Number and width of lands and grooves in the rifling

10. Gunshot Residue and Wounds

Range of Gunshot

  1. Distant Shots

    • No detectable GSR on the victim.

    • May show a bullet wipe.

  2. Close-Range Shots

    • Two types of GSR deposits: Stippling and Soot.

  3. Near-Contact Shots

    • Stippling and smudging present; possible damage to clothing.

  4. Contact Shots

    • Jagged entrance wounds; potential for GSR particles to enter the wound.

11. Problems in Firearms Identification

  1. Determining caliber/type of firearm from bullets or cartridge cases.

  2. Identifying if a bullet or cartridge case was fired from a suspected firearm.

  3. Confirming if multiple bullets or cases were fired from the same firearm.

  4. Determining if a firearm is serviceable.