Date of Graduation
Eberly College of Arts and Sciences
Forensic and Investigative Science
In the U.S., although this technique has been in use for many years, there is still debate as to what constitutes GSR. When the firing pin strikes the primer, the priming compound is compressed and detonates since it is sensitive to percussion. This, in turn, causes the propellant to ignite and build up pressure within the cartridge case. When sufficient pressure is built up the bullet will be forced down and out of the barrel. The compounds chosen for this formulation are mainly inorganic in nature. Many of the components will be vaporized during ignition because of the extremely high temperatures. Upon the exit of the bullet from the barrel, the gases and vapors will escape through the various openings. When these vapors are exposed to a rapid decrease in pressure and temperature, they will condense and the generated particles will be deposited on the person of the shooter or someone in close proximity. Particles that land on the shooter are collected and analyzed using the scanning electron microscope/energy dispersive spectroscopy (SEM/EDS). The objective of the study was to evaluate the persistence of gunshot residue particles on the hands of a shooter. Shots were fired by four volunteers who were sampled for GSR at various times after the shooting. A 1 cm piece of carbon tape (Ted Pella Inc) was placed on a 1 cm aluminum stub and samples were collected from the back of the hand. These samples were analyzed using the SEM/EDS. The persistence of unique gunshot residue particles over a time frame of 0--180 minutes was evaluated. Analyses of these 22 samples from two of the volunteers using the 9mm pistol were analyzed by manual analysis. Results show that over the selected time frames there is a decrease in the number of unique GSR particles collected on the hands of a shooter after approximately one hour.
Wallace, DeAnna M., "Transfer and Persistence of Gunshot Residue Particles" (2010). Graduate Theses, Dissertations, and Problem Reports. 4667.