Gunshot residue (GSR) analysis is a standard method to determine if a firearm has been used. Particles for GSR analysis typically range from 0.5 to 10 microns. Often the primer particles containing lead (Pb), barium (Ba) and antimony (Sb) are detected and analyzed using EDS in a scanning electron microscope. Titanium (Ti) and zinc (Zn) are becoming more common as lead-free ammunition. To be statistically valid, imaging and analysis are automated to process multiple samples in an SEM.
An example spectrum from one particle is shown here. Multiple particles and spectra are required for full analysis. Using the Phenom desktop SEM for GSR, up to 36 sample stubs can be automatically imaged and analyzed in one session.