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Analysis of gunshot residue (GSR). Forensic scientist using a scanning electron microscope (SEM) to search for GSR particles (not seen) on a sample from a suspect. The SEM display is the black screen. The machine at left is the SEM-EDX analyzer, which combines the SEM analysis with an X-ray beam energy dispersive analysis (EDA or EDX). The EDX display (far right) will reveal the presence of the lead, antimony and barium that is found in GSR. GSR is formed when firing 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 tiny GSR particles. They are deposited on the hand and clothes of the shooter. (KEYSTONE/SCIENCE PHOTO LIBRARY/MAURO FERMARIELLO) === ===