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Examination of Firearms
retrieved Feb 11, 2020, https://firearms-examiner…
Examination of Firearms
retrieved Feb 11, 2020, https://firearms-examiner.training.nij.gov/
Module 8
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Evidence Receipt
- Each firearm should be properly packaged and accompanied by documentation providing details of the incident and the examinations requested
- marked according to laboratory protocol prior to conducting any examinations
Examination Documentation
- must be complete and accurate
- effective work habits
- laboratory protocol
Firearms Identification Information
- Brand name or trademark
- Serial number
- Model designation
- Caliber designation
- Importer, if applicable
Military Firearms
- typically do not have a caliber designation
- symbols and codes identify the manufacturer
Proof Marks
- older foreign manufactured firearms will list a location, rather than a manufacturer
- there are a number of reference books that display proof marks and their meanings
Examination
- firearm is unloaded
- brand, model, and caliber designation
- action type and safety type
- modifications or alterations
- sighting system and any accessories present
- examine the bore
- test the trigger pull, the safety feature, and test firing of the mechanism
Safety Features
- General safety procedures
In the laboratory...
- be aware of all safety policies and procedures
- be responsible for your own safety and of others
- handle every firearm as if it is loaded unless checked
- follow the procedure for the particular laboratory
Always keep...
- a firearm pointed in a safe direction
- finger off the trigger until ready to shoot
- firearm unloaded until ready to use
Passive Safety Features
- called a disconnector
- disconnects the trigger from the firing mechanism
If safety features are functioning:
- The hammer catches at the half-cock
- The transfer bar drops away from the firing pin
- The hammer block engages
If the primed case detonates:
- safety is not functioning properly; retest the firearm
- If the primed case detonates after retesting, improper function of the safety is confirmed
- The test was not performed properly; retest the firearm.
- There is no safety feature present; examine the interior of the firearm to determine if a safety feature was present and subsequently removed.
Test Firing
- Function
- Bullet Recovery
- Additional Testing
Revolvers
- double-action revolvers with the capability of operating in single- or double-action mode, test fires should be obtained using both modes
Multi-barreled firearms
- each barrel must be test fired
Rifles
- can present difficulties in the recovery of fired bullets
Firearms unsafe to discharge
- cast the barrel or the breech face firing area to provide microscopic detail for examination and comparison
Drop Testing
- When firearms submitted to the crime laboratory are involved in an alleged accidental discharge case
drop test examination:
- Place a one-inch-thick rubber pad onto a solid floor (such as concrete).
- Place a primed cartridge case in the chamber that will receive the hammer strike.
- Cock the firearm.
- Disengage the external safety.
- Drop the firearm from a height of about three feet onto the pad.
Test all positions of the firearm - top, bottom, left side, right side, rear, and muzzle
The primed case detonates:
- Field strip the firearm.
- Examine the major internal components to determine if there are any broken or missing parts.
The primed case does not detonate, indicating that the firearm will not discharge when dropped
Shock Test
- conducted using a dead blow hammer
- firearm is struck with the dead blow hammer
Visual Examination
- Type of magazine
- Type of action
- Caliber designation
- Telescopic sights - recorded
- Safety