Gunshot residue (GSR) is the collective term for the cloud of fine debris that is expelled from a firearm when a round of ammunition is discharged. It is also known as FDR (firearms discharge residue) or CDR (cartridge discharge residue). The cloud may contain a mixture of metallic and nonmetallic particles.

Metallic particles originate from the primer charge, bullet, cartridge case and barrel. Nonmetallic particles originate from the propellant, deposited as unburnt or partially burnt particles.

Only particles from the primer are considered to be characteristic of GSR. Particles from the bullet, cartridge case and barrel are either indicative or commonly associated with, but on their own are not exclusive to, GSR.

GSR particles can persist on some materials for a considerable amount of time.

Forensic analysis involves the careful recovery of the microscopic metallic particles from clothing, surfaces or directly from the skin or hair of an individual. The samples are coated with a thin layer of carbon and then examined for their characteristic elemental composition and morphology using a powerful scanning electron microscope (SEM). Cellmark’s SEM and software is the latest generation of SEM specifically designed for the rapid analysis of GSR particles.

GSR can provide supporting evidence for an investigation involving firearms and can help to determine:

Whether a person has been exposed to the discharge of a firearm, (either by discharging a gun or being in close proximity to a discharging gun)
Whether a gun was fired from or towards a particular location
Whether a particular person has been in possession of or handled a gun
Whether firearms have been carried or stored in vehicles
Whether vehicles have been used as getaway vehicles
Which clothing was worn by the firer
The range and type of projectile that was used