![]() proposed a classification of gunshot residue based on composition, morphology, and size. ![]() If the scanning electron microscope is equipped with an energy-dispersive X-ray spectroscopy detector, the chemical elements present in such particles, mainly lead, antimony and barium, can be identified. In 1971 John Boehm presented some micrographs of gunshot residue particles found during the examination of bullet entrance holes using a scanning electron microscope. This approach, introduced in 1933 by Teodoro Gonzalez of the Mexico City Police Laboratory, is called dermal nitrate or paraffin test and is no longer used in casework. The cast was then sprayed with a reagent giving a coloration with nitro-compounds from the partially burnt and unburnt propellant particles. Depending on the type of fire arm and ammunition used, it will typically travel no farther than 3–5 feet (0.9–1.5 meters) from the muzzle of the gun.īefore the use of the scanning electron microscope, hot paraffin wax was used to take a cast of the suspect’s hand. ![]() Gunshot residue does not travel very far because the particles produced are of a small size and small mass, causing them to lack momentum. Law enforcement investigators will swab people's hands to look for gunshot residue if they are suspected to have discharged a firearm themselves or were in close contact with one at the time discharge. A graphic representation of the GSR left on a target when fired upon from varying ranges.
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