How We Investigate: Firearms/Toolmarks Unit
Firearms/Toolmarks Unit
The Firearms/Toolmarks Unit (FTU) received and handled the evidence related to the screwdriver found in the bag and the piece of metal found at the scene.
The evidence examined by the FTU was first prepared for analysis, by weighing and photographing the screwdriver. In addition to these preliminary examinations and research conducted by technicians and the microscopic analyses performed by examiners, the evidence underwent a variety of testing.
Toolmark examinations of the screwdriver also required an examiner to make casts of impressions left by the tool. A clay dam was created around the toolmarked area (in this case, on the doorjamb) and an epoxy, or plastic casting material, was poured into the area.
The detail obtained with this procedure was so good that once the cast had set and dried, it could be examined and compared microscopically with the broken tip of the screwdriver that was found inside the door of the building. They matched.