Firearms and Toolmark Examination is a discipline of forensic science that deals with the examination of firearms and the evidence discharged from firearms that are recovered at shooting incidents.

The majority of a firearm and toolmark examiner’s work requires microscopic examination of bullets and cartridge cases recovered at shooting incidents. Upon determining the suitability of an item for examination, the examiner may be able to determine if one or more firearms were used to discharge the evidence recovered at the shooting incident. If a specific firearm is also submitted for examination, the examiner may be able to generate test bullets and cartridge cases from the firearm and use them in a comparison to the recovered evidence. The examiner may then be able to determine if that specific firearm was used to discharge the recovered evidence or not.

Firearms Examiners use a comparison microscope to analyze microscopic details imparted onto the bullets and cartridge cases. It is those microscopic details in the same relative position of the discharged ammunition components that allow an examiner to conclude if more than one firearm or a specific firearm was used to discharge them.

The firearm and tool mark unit also performs functionality determinations on firearms submitted in violent crime cases. The laboratory utilizes an indoor firing range or a water tank when test firing firearms. Known standards are collected from submitted firearms and can be later compared to fired bullets and fired cartridge cases collected at shooting incidents. The laboratory does not perform function testing on firearms from routine firearm seizures leading to gun possession chargers or firearms seized for safe keeping. The laboratory will accept test cartridge cases from external test fires of these firearms for entry into the National Integrated Ballistic Identification Network (NIBIN). The laboratory will perform function testing on firearms where there is clear suspicion or link to shooting incident, a potentially malfunctioning or inoperable firearm, or a modified firearm.

Serial number restorations using polishing, acid etching, and magnetic particle inspection can be performed by the unit on firearms where the serial number has been obliterated or otherwise defaced.

Additionally, the firearms unit is partnered with the Bureau of Alcohol, Tobacco, and Firearms (ATF) in the usage of the National Integrated Ballistic Information Network (NIBIN).

NIBIN is a computer system that makes a digital image map the toolmarks imparted onto a cartridge case head and primer when it is fired by a firearm. The computer is designed to use those digital images to provide potential links between incidents where the same firearm may have been involved or to an incident where the firearm that discharged the evidence may have been recovered. The links, or NIBIN Leads, generated by the system are preliminary in nature and require confirmation through a microscopic comparison. The unit meets the Gold Standard of ATF’s Manufacturer’s Recommended Operations Standards as of the last external assessment.

Links:

• The Association of Firearm and Tool Mark Examiners (AFTE)
• National Integrated Ballistic Information Network (NIBIN)
• Bureau of Alcohol, Tobacco, Firearms, and Explosives
• American Board of Criminalistics (ABC)
• American Society of Crime Laboratory Directors, Laboratory Accreditation Board (ASCLD)
• The American Academy of Forensic Sciences (AAFS)
• The Midwestern Association of Forensic Scientists (MAFS)
• Criminal Justice Information Service