Identification of Both Inorganic and Organic Gunshot Residues on a Firearm and Its Applications

Abstract

Gunshot residues (GSR), which mainly consist of fired primer compound and propellants, remaining on a firearm were investigated by electron probe microanalyzer (EPMA) and Fouriertransform infrared spectroscopy equipped with a microscope (FT-IR). Sample collection and handling techniques were developed to analyze of GSR, both inorganic and organic components. The sample was washed with n-hexane at first. The obtained waste solution was filtered with a white membrane filter made from polyterafluoroethylene. Spherical particles and shapeless particles in various sizes and colors on the membrane were observed under an optical microscope with about 75 magnification. Lead, antimony and barium were usually detected from the spherical particles using EPMA, and it indicated that spherical GSR came from primer compound. On the other hand, shapeless particles were picked up using a fine needle and identified by FT-IR. This method was applied to a hand of a gun shooter and a shirt of the killed woman. The inorganic GSR was detected from the hand of a gun shooter and the organic GSR was found from the shirt. These procedures have some advantages, they are very simple, rapid, inexpensive, non-destructive and detected both primer compound and propellant.