Introduction

It is impossible to discharge a firearm without leaving behind evidence. Apart from the actual bullet, a lot of smoke emerges from multiple areas of the gun, and will inevitably end up on the shooter's hand and other surfaces. This smoke is called gunshot residue (GSR). It is made up of particulate matter, or microscopic particles, which settle on any surface they come in contact with and adhere because of electrostatic and van der Waals forces.

In forensic science, the gunshot residue is collected for analysis, both from the victim around the entry wound and from potential suspects' hands, arms, faces and clothing. The particles can be analyzed using a variety of methods, but electron microscopy (EM) has proven to be the most effective. Using EM and energy-dispersive analysis of x-rays (EDAX), an investigation was conducted on the gunshot residue from four different types of ammunition to determine whether the residue could be uniquely identified.