Firing a gun causes combustion of both the primer and powder of the cartridge (Examination of gunshot residue).
This energy causes numerous metallic elements found in the weapon to become a vaporized cloud, which can then be deposited on the both the shooter and the victim (Firearms Residue, 2011). The invisible particles that crime scene investigators look for are generally the cooled composition of antimony, barium, and lead deposited on any surface close to the weapon when fired (Firearms Residue, 2011; Locke, 2012). "Less common elements include aluminum (Al), sulfur (S), tin (Sn), calcium (Ca), potassium (K), chlorine (Cl), copper (Cu), strontium (Sr), zinc (Zn), titanium (Ti), or silicon (Si)" and some "so-called 'lead free' ammunition may contain one or more elements including strontium (Sr), zinc (Zn), titanium (Ti), copper (Cu), antimony (Sb), aluminum (Al), or potassium (K)" (Examination of gunshot residue). "Some common places that the forensic teams collects samples for gunshot residue analysis include "the hands, face, clothing of the shooter and on the weapon itself" (Firearms Residue, 2011). Firearm residue can also be found on the victim and any bystanders (Locke, 2012). .
"The major methods for detection of primer residues are analytical and qualitative. Analytical methods include neutron activation analysis (NAA) as well as atomic absorption spectrophotometry (AAS) and inductively coupled plasma mass spectroscopy (ICP-MS)" (Examination of gunshot residue). Qualitative methods include scanning electron microscopy with energy dispersive analysis by x-ray detector (SEM-EDX) and atomic force microscopy (AFM) (Examination of gunshot residue). Prior to 1995, the presence of firearm residue was determined similar to the way that they show on television (Locke, 2012). There are two methods used to collect gunshot residue: collection into carbon- coated adhesive stub or with an alcohol swab (Examination of gunshot residue).