MAURO FERMARIELLO / SCIENCE PHOTO LIBRARY MAURO FERMARIELLO / SCIENCE PHOTO LIBRARY
Looking for gunshot residue (GSR). GSR stub being used to sample a suspect's hand. GSR is produced during the firing of a gun. Various materials are used in the explosive mix that fires a bullet, and these are ejected from the gun in a cloud of GSR. This is deposited on the hand and clothes of the person who fired the gun, and on the surroundings. The stub has an adhesive surface that collects any GSR present. The stub is placed in an X-ray beam energy dispersive analyzer (EDA or EDX) to detect any lead, barium and antimony. A positive result indicates that the suspect fired a gun recently. GSR is fragile and easily removed, so sampling is done within hours of a shooting.
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