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Gunshot residue particle velocity and deceleration
Peter R De Forest1, Kirby Martir, Peter A Pizzola
1John Jay College of Criminal Justice, 599 Tenth Avenue, New York, NY, USA.
Journal of Forensic Sciences
|December 1, 2004
Summary
Gunshot residue particles travel at high velocities (500-600 ft/sec), explaining stippling on nearby surfaces. Rapid deceleration limits their travel distance, with minimal impact from air currents near the muzzle.
Area of Science:
- Forensic Science
- Ballistics
- Physics
Background:
- Understanding gunshot residue (GSR) particle behavior is crucial in forensic investigations.
- The velocity and trajectory of GSR particles influence their deposition patterns and the interpretation of crime scenes.
Purpose of the Study:
- To determine the velocity of gunshot residue particles.
- To investigate the factors affecting GSR particle travel and deposition.
- To explain phenomena like stippling and particle distribution near a firearm's muzzle.
Main Methods:
- Utilized high-speed stroboscopic photography with a spark gap light source.
- Analyzed the velocity of over 800 gunshot residue particles from eight distinct sources.
- Calculated particle deceleration over a 100-microsecond interval.
Main Results:
- Average GSR particle velocity ranged from 500 to 600 ft/sec, with some exceeding this range.
- High velocities enable particles to embed in nearby materials like skin and fabric.
- Rapid deceleration was observed, limiting particle travel to approximately 3 ft from the muzzle.
- Air currents showed minimal influence on particle behavior near the muzzle.
Conclusions:
- The high initial velocity of GSR particles explains stippling formation on skin and fabric close to the muzzle.
- Rapid deceleration accounts for the limited range of GSR particle detection.
- Environmental factors like normal wind velocity are unlikely to significantly alter GSR particle trajectories near the firearm.