Gunshot Residue

When a gun is fired, gases from the exploding materials contain particles from the explosion, especially the primer material, that can then condense on the shooter’s hands or clothing. Most of these particles are not visible to the naked eye, so police use adhesive lifters to remove the particles for testing. Special spectroscopic instruments known as scanning electron microscopy coupled with energy dispersive X-Ray spectrometry (SEM-EDS) can identify chemicals that are typically used in gunshot primers, such as lead, barium, and antimony. Testimony that gunshot residue was found on the defendant’s hands or clothing is often admissible, but there are limitations and concerns. The chemical particles are not unique to primers and may come from other sources, and there are no standards for determining how many particles are required to allow a gunshot residue conclusion. A gunshot residue analyst also cannot describe how or when the chemical particles were deposited.