Medical Examiner

Firearms/Toolmarks

The Firearms/Toolmarks Section performs a variety of functions for law enforcement agencies within Allegheny County. The types of examinations available include:

Firearms: A routine operability and safety inspection is performed before test firing each firearm. The test cartridge cases from select caliber firearms are entered into the NIBIN system and the test bullets and cartridge cases are compared to bullets and cartridge cases in the "open case file".

NIBIN: Through the National Integrated Ballistic Information System, the Bureau of Alcohol, Tobacco, Firearms & Explosives deploys Integrated Ballistic Identification System (IBIS) equipment into Federal, State and Local law enforcement agencies for their use in imaging and comparing cartridge case and bullet evidence. The goal of NIBIN is to discover links between crimes more quickly. For more information on NIBIN visit World Wide Web Icon www.nibin.gov.

Currently, the Medical Examiner’s Office only captures images from cartridge cases. IBIS facilitates the acquisition and automated initial comparison of digital images captured by Allegheny County, Pennsylvania State Police and Philadelphia Police Department. Should a “high-confidence” candidate arise, the Firearms Examiner will confirm the “match” between the cartridge cases from the incidents. Since August 1998, over 1386 “links” have been made.

Open Case File: The open case file consists of bullets, cartridge cases and shotshell cases that were found at crime scenes and where no firearm was recovered. The open case file is organized according to caliber and rifling characteristics. Identifications to the open case file may average one per week. These identifications link different incidents to the same firearm and can provide investigators with possible leads.

This section is one of the few Firearms Sections which actively maintain an Open Case File Search that has resulted in 110 identifications since May of 2006.

Fired Components: Spent bullets, cartridge cases and shotshells are classified and, if they have sufficient detail, are compared to those fired components already in the open case file. If no identifications to the open case file are made, the fired component will be placed in the open case file.

Gun Shot Residue: The gunshot residue kits (hand swabs) are presently tested using Atomic Absorption Spectrophotometry. The analysis looks for certain chemical elements found in the primers of most cartridges. If the elements are present and in the proper ratios, the person in question may have discharged or handled a firearm.

Clothing: Articles of clothing are examined for any firearms related evidence such as bullet holes, soot or smoke, gun powder particles and bullet wipe. Distance determinations can also be made by examining the powder particle pattern on the clothing and comparing it to test patterns produced using the weapon used in the incident.

Toolmarks, Shoeprints, Tireprints: All are examined to determine class characteristics and suitability for comparison. If the evidence toolmark, shoeprint or tireprint is suitable and a questioned item (tool, shoe, or tire) has been submitted, a comparison will be made to determine if the questioned item was used in the incident.