Thanks to all the crime scene shows on television today, almost everyone is aware of gunshot residue. In the shows, like CSI, we can see a crime scene investigator swab a suspect's hands for an invisible powder and then place the swab into a liquid chemical to see if there is a color change. If there is a color change, it means that there are GSR particles present on the suspect's hands. However, real life is never that simple. By looking at the actual science behind GSR, we can see that it gunshot residue analysis is not as cut and dry as the television shows make it seem. There are actually many problems with the process and results gunshot residue analysis that are not depicted on television, making it better for only preliminary testing in the forensics investigation.
GSR, also known as firearm residue, is defined as the "residue from the primer that is produced when a gun is fired" (James, Nordby, & Bell, 2014, p. 572; Firearms Residue, 2011). After a bullet or cartridge is fired, the residue gets deposited on the hands of the shooter, as well as on the victim, something most us already know thanks to CSI ("Firearms Residue," 2011). But where does firearm residue come from? Well, when a weapon is discharged, a series a reactions occur in the barrel of the gun, releasing a large amount of heat energy (Firearms Residue, 2011). "The burning rate of gunpowder can be classified in three categories: degressive (regressive) burning, neutral burning, and progressive burning" (Examination of Gunshot Residue). Degressive or regressive burning consists of gunpowder grains formed in flakes, balls, and sticks that have a burning surface area that decreases continuously as the grains are consumed (Examination of gunshot residue).The gunpowder grains that are single holed and the burning surface area remains mostly constant is called neutral burning; while progressive burning is when "gunpowder grains that are multi-perforated and rosettes that have a burning surface area that increases continuously as the grains are consumed" (Examination of gunshot residue).
