- U.S. Department of Justice
- Federal Bureau of Investigation
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in the FBI Laboratory |
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Forensic Science Communications Forensic Science Research Unit Federal Bureau of Investigation Washington, DC |
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Evidence in a typical case may include a number of recovered rifles, pistols, shotguns, silencers and other muzzle attachments, magazines, holsters, and a variety of fired and unfired cartridges. Lead and other metal fragments, shot wads, shot cups, and bullets removed from bodies at autopsy are also frequently received items in firearms-related casework. Evidence submitted in toolmark cases may include screwdrivers, scissors, knives, pliers, wrenches, crowbars, hammers, saws, wire, sections of sheet metal, chains, safety-deposit boxes, human bone or cartilage, plates, locks, doorknobs, bolts, and screens. In addition to the preliminary examinations and research conducted by technicians and the microscopic analyses performed by examiners, evidence in the Firearms-Toolmarks Unit may undergo a variety of testing. Depending on the specifics of the case and the examinations requested by a contributor, an examiner-technician team may employ the following tests and procedures: |
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Firearms evidence: cartridges, casings, and bullets |
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The presence of gunpowder
on items of evidence can be determined through gunshot residue examinations. |
Toolmark examinations may also require an examiner to make casts of stamped numbers or impressions. These are made by creating a clay dam around the toolmarked area and pouring an epoxy or plastic casting material into the isolated region. Although some casts are made solely for reference purposes, the quality of detail obtained with this procedure is such that once a cast has set and dried, it can be examined and compared microscopically with other toolmark casts and questioned tools. For more information on casting techniques, see the Shoeprint and Tire Tread Examinations and Serial Number Examinations sections of the Handbook of Forensic Services.
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The Firearms-Toolmarks Unit
examines Vehicle Identification Numbers (VINs; above right) and
other stamped serial numbers for the presence of criminal alterations.
Die stamps, such as the X character shown above left, and other
equipment used to produce identifying characters may be examined
in serial number restoration cases. |
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Firearms-Toolmarks Unit personnel have contributed to investigations surrounding such high-profile cases as the assassination of Martin Luther King, Jr., the assassination of John F. Kennedy, the attempted assassination of Ronald Reagan, Ruby Ridge, Waco, the Oklahoma City Bombing, and the Centennial Park Bombing, but the majority of casework in the FTU involves what might be considered to be more typical crimes. With regard to any case, however, filing the final report and mailing back the evidence do not necessarily represent the end of the Firearms-Toolmarks Unit's involvement in federal or local investigation. Firearms examiners are often called upon to testify to the results of their examinations as expert witnesses in criminal proceedings. Physical evidence ranging from firearms and ammunition components, tools and toolmarked items, obliterated serial numbers, silencers, and gunshot residue may confront these forensic specialists in a court of law. Though FTU examiners may serve as expert witnesses for either the prosecution or the defense, the FBI prohibits the testimony of its examiners in cases where other expert firearms- or toolmarks-related testimony is already being or has been provided.
Firearms examiners provide field support in FBI investigative matters and administrative inquiries, directing or assisting with the collection, preservation, and processing of evidence at crime scenes. In addition, field teams from the Firearms-Toolmarks Unit provide crime scene reconstructions and analyses as needed, stateside or internationally, with designated response teams on standby rotation in the event of disaster in the United States or overseas.
The FTU also serves as a liaison with national and international forensic laboratories. Examiners from this unit provide extensive training services, both general and specialized, to members of law enforcement agencies as well as to crime scene personnel and investigators. Training schools in trajectory analysis, gunshot residue analysis, firearms identification, and the identification of stolen motor vehicles are sponsored by the FTU on a yearly basis, often with multiple classes being offered in different cities throughout the year.
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The identification of stolen
motor vehicles may involve trucks and construction equipment as well as motorcycles, cars, and watercraft. FTU-sponsored training schools provide information on the location of serial numbers and how to determine whether they have been criminally altered. |
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Bullet trajectory analysis
provides information about the location or positioning of a shooter and the direction of fire. This photograph demonstrates how firearms examiners document the flight paths of individual bullets with regard to entrance and exit holes. |
For more information about
the Firearms-Toolmarks Unit, call or write:
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Federal Bureau of Investigation Telephone: 202-324-4378 |
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FORENSIC SCIENCE COMMUNICATIONS APRIL 2000 VOLUME 2 NUMBER 2
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