ISSN: 0022-1198
CODEN: JFSCA
Published Online: 1 November 2004
Page Count: 7

Gunshot Residue Particle Velocity and Deceleration
Martir, K
Supervisory Forensic Chemist, DEA Northeast Laboratory, NY

Pizzola, PA
Supervisory Criminalist (IV), NY

De Forest, PR
Professor of Criminalistics, John Jay College of Criminal Justice, NY

(Received 21 April 2003; accepted 3 July 2004)

Abstract

The velocity of over 800 gunshot residue particles from eight different sources was determined using high speed stroboscopic photography (spark gap light source). These particles were found to have an average velocity of 500 to 600 ft per second. Many particles acquired considerably higher velocities. Thus, the particles have sufficient energy to embed themselves within certain nearby targets like skin or fabric. The relatively high velocity that the particles acquire explain the formation of stippling on skin in close proximity to a muzzle discharge. These findings also indicate little influence of air currents on particle behavior near the muzzle. The deceleration of less than 100 particles during a 100-microsecond interval was also calculated. The particles experienced rapid rates of deceleration which would explain why few particles are found in test firings beyond 3 ft from the muzzle of a discharged firearm. Because of their relatively high velocity, normal wind velocity would not be expected to significantly influence their motion near the muzzle.

Keywords:
forensic science, criminalistics, gunshot residue, firearms discharge patterns, propellant particles, velocity, deceleration, stippling, high-speed stroboscopic photography

Paper ID: JFS2003137
DOI: 10.1520/JFS2003137
ASTM International is a member of CrossRef.