The use of unburned propellant powder for shooting-distance determination. Part I: Infrared luminescence

- Infrared luminescence inspection of gunshot residue is an easy and reliable method for the detection of propellant particles in target tissue for about 80-90% of ammunition types. The quantification of unburned propellant particle densities can be used to draw shooting distance curves. The curve slope strongly depends on the morphology of the propellant particles. Muzzle-to-target distances could be determined up to 1.5 m for pistols and up to 3 m for a revolver.
- In cases of large particle density variation within the samples of identical shooting distances, the ratio of the amount of particles within the area around the bullet hole and within a ring with a defined distance from the bullet hole was calculated. These data resulted in measures with much lower standard deviations.
- The described method can be applied as a supplementary method on the same samples before or after the Rhodizonate Test or the Chlorindazone Test.

Unburned propellant powder particles in gunshot residue (GSR) were detected at near infrared by optical excitation in the visible wavelength range. A series of ammunition (different brands and different manufacturers) was analyzed concerning the luminescence of their propellant.Shooting target samples with different shooting distances were produced on standard textile tissue and analyzed with this optical infrared inspection. The number of luminescent GSR particles per area was measured and curves with particle density vs. shooting distance were drawn.The method was applied on three ammunition types with different particle morphology shot with a pistol and one ammunition type shot with a revolver. The shooting series performed with the revolver showed a large particle density variation within the samples of identical shooting distances. In this case, the ratio of the amount of particles within the area around the bullet hole and within a ring with a defined distance from the bullet hole was calculated. These data resulted in measures with much lower standard deviations, which is a prove that the distribution pattern depends on the shooting distance and not on the amount of GSR particles.It has been shown, that imaging of target tissue with the aid of infrared luminescence is an easy, fast, reproducible and non-destructive method for shooting-distance determination.