Firearms Identification and Evidence Collection

Firearms Identification Science

  • Purpose: Determines if a particular bullet was fired from a particular gun.

  • Scope: Also applies to cartridge casings and shotgun shells.

Firearm Evidence Collection - General Considerations

  • First Consideration: Safety

    • Assess if the firearm can be transported loaded.

    • If not, unload the firearm with extreme care.

  • Preservation of Other Evidence

    • Always consider and preserve other potential evidence alongside the firearm, such as:

      • Fingerprints

      • Blood

      • Fibers

      • Debris

Collecting Firearm Evidence - Documentation and Handling

  • Documentation:

    • Photograph the firearm as found.

    • Take detailed notes.

    • Create sketches.

  • Handling to Preserve Prints:

    • Firearms may contain latent fingerprints.

    • Handle the weapon carefully by:

      • Checkered grips

      • Sides of the trigger guard

      • Knurled or rough surfaces

  • Marking Weapons:

    • Serialized Weapons:

      • Identify by recording the manufacturer's serial number.

      • Photograph the serial number.

      • A Sharpie marker can be used to initial the weapon, following departmental procedure (which may also require etching).

    • Un-serialized Weapons:

      • Require marking for identification.

      • Mark or etch the weapon with the initials of the investigator who collected it, as per departmental procedure.

Unloading Revolvers

  • Prior to Moving Cylinder:

    • The cylinder should be marked to indicate its position as found upon recovery.

    • A diagram should be made by the officer recovering the weapon, illustrating the appearance and contents of the cylinder as recovered.

  • Cylinder Rotation Direction:

    • Smith & Wesson (S&W): Rotates counter-clockwise (CCW).

    • Colt Revolver: Rotates clockwise (CW).

    • Historical Note: S&W obtained the patent for their revolver first, leading Colt to change their design to secure a patent. After 7 years, any manufacturer could choose the direction. Today, most weapons are CCW.

  • Detailed Cylinder Documentation (Example):

    • An investigator should mark each chamber's contents and position.

    • Columns for documentation might include:

      • Investigator's Mark (e.g., M1, M2)

      • Location in Cylinder (e.g., 1, 2, 3, 4, 5 corresponding to chambers)

      • Description (e.g., Fired, Live)

      • Manufacturer and Type (e.g., R-P, JHP; Federal, lead; RN)

      • Direction of Rotation (indicated on diagram)

    • Reference: Lee, H.C., Palmbach, T., & Miller, M.T. (2001). Henry Lee's Crime Scene Handbook. San Diego, CA: Academic Press.

Unloading Single Shot or Autoloading Firearms

  • Point in Safe Direction: Always ensure the firearm is pointed in a safe direction.

  • Remove Magazine: The magazine should be removed first.

  • Examine Chamber:

    • Visually examine the chamber.

    • Clear the chamber by slowly drawing back the slide/bolt handle.

    • Visually examine the chamber again to confirm it is clear.

  • Packaging:

    • Separately package the firearm, magazine, and any extracted cartridges or cases.

    • Do not remove cartridges from the magazine during collection.

    • Do not mark cartridges or cases directly at the scene.

Special Handling of Firearm Evidence

  • Loaded Firearms:

    • Make safe at the scene if possible.

    • Otherwise, personally transport the loaded firearm with extreme caution.

  • Firearms Found in Water:

    • If a firearm is found in water, transport it with the same water to prevent rust and loss of trace evidence.

  • Actions to Avoid:

    • Do not make any adjustments to the firearm.

    • Do not test fire the weapon at the scene.

Firearms Comparisons

  • Purpose: To compare questioned evidence (bullets, cartridge cases) to known samples (test-fired bullets, cartridge cases).

  • Bullet Comparison:

    • Test-fired bullets may yield both class characteristics (e.g., caliber, number/direction of lands and grooves) and individual characteristics (unique striations from the barrel).

  • Cartridge Case Comparison:

    • Can reveal individual characteristics such as:

      • Firing pin impressions

      • Extractor marks

      • Breech face markings (from the breech face of the firearm).

Packaging Bullets and Cartridge Cases

  • Individual Packaging: Place each bullet and cartridge case in separate envelopes or bags.

  • Protection:

    • Protect all striations and marks (essential for comparison).

    • Protect any potential fingerprints, residue from the barrel, or other trace evidence.

  • Immobilization: Immobilize items for transportation to prevent damage.

  • Material: Package in paper envelopes or small boxes.

  • Reference: Lee, H.C., Palmbach, T., & Miller, M.T. (2001). Henry Lee's Crime Scene Handbook. San Diego, CA: Academic Press.

Information from Evidence Bullet

  • Identifiable Information:

    • Manufacturer

    • Caliber

    • Shape (e.g., hollow-point)

    • Composition

    • Individual marks from the barrel (lands and grooves)

    • Type of weapon (inferred from class and individual characteristics)

Removal of Embedded Bullets

  • Bullets Embedded in Wood or Plaster:

    • Do not attempt to dig the bullet out directly.

    • Remove the bullet by cutting out the portion of material in which it is embedded.

    • Send the material containing the bullet to the laboratory.

  • Removal of Evidence Bullet from a Deceased Person:

    • Bloody Bullets: Wash gently without scrubbing.

    • Do not wash if trace evidence (e.g., fabric, biological material) might be present.

    • Dry bullets thoroughly prior to packaging.

    • Package each bullet separately.

    • Crucial: Do not mark the bullet itself. Instead, mark the sealed container with a description of the bullet.

Information from Fired Cartridge Cases

  • Identifiable Information:

    • Manufacturer

    • Caliber

    • Type (rimfire or centerfire)

    • Extractor marks

    • Firing pin mark

  • Location of Ejected Casings:

    • The location of ejected cartridge casings can help to determine the approximate position of the shooter.

    • Make a detailed sketch with accurate measurements of the location of fired cartridge cases.

Shotgun Evidence (Wads and Pellets)

  • Shot Wads:

    • When a shotgun is fired, the wad travels along with, or just behind, the shot for a short distance.

    • In close-range shootings, wadding may be found embedded in the victim's body or clothing.

  • Shot Pellets:

    • Pellets Embedded in Material (wood, plastic, etc.): Handle in the same manner as bullets; cut out the surrounding material and submit to the lab.

    • If Submission is Not Possible: Pellets may be carefully dug out. Use special care to recover pellets without undue damage.

Collection of Loaded Shells or Cartridges

  • Submit All Ammunition: Collect and submit to the laboratory all ammunition associated with the case.

  • Purpose: This ammunition can be used for test firing and distance determinations.

  • Documentation: Document precisely where the ammunition was found.

  • Packaging:

    • Large quantities should be placed in a cardboard box or wooden container.

    • Label, seal the container, and deliver it to the laboratory.

Ballistic Identification Systems

  • DrugFire:

    • A multimedia database imaging system developed by MSI (Mnemonic System Inc.).

    • Automates the comparison of images of bullet cartridge cases, shell casings, and bullets.

    • Allows examiners across the United States to compare and link evidence from spent cartridges and other ammunition casings.

  • IBIS (Integrated Ballistic Identification System): A comprehensive system for ballistic imaging.

  • NIBIN (National Integrated Ballistic Information Network): A national database that incorporates IBIS technology, allowing for comparisons of ballistic evidence across jurisdictions.

Serial Number Restoration

  • Principle: Serial numbers are typically impressed into the metal body or frame of a firearm. The force exerted by a steel die extends a short distance below the original surface number.

  • Obliteration Methods: Numbers can be removed or obliterated by grinding, rifling, or punching.

  • Restoration Method: Etching Reagents

    • Mechanism: The strained area of the metal where the number was impressed dissolves faster than the unaltered metal.

    • Procedure:

      1. Clean the area thoroughly.

      2. Polish the area to a mirror-like surface.

      3. Swab the appropriate etching reagent onto the area with a cotton ball.

    • Reagent Depends on Surface Material:

      • Steel Solutions: A mixture of hydrochloric acid, copper chloride, ethanol, and water.

      • Aluminum Solutions: Aqueous sodium hydroxide.

      • Zinc Alloy Solutions: Alternating applications of phosphoric acid - nitric acid solution and 5 - 10\% nitric acid.

    • Example: A photograph shows a restored serial number, e.g., 1875622

  • Issues/Limitations in Restoration:

    • The entire "zone" of the impressed number has been removed.

    • Too much metal has been removed.

    • The original number has been impressed with another number over it.