Gunshot residue on dark materials: a comparison between infrared photography and the use of an alternative light source
The pattern of gunshot residue (GSR) includes important information about muzzle-target distance since a larger GSR distribution diameter indicates a larger shooting distance. GSR may not be visible to the naked eye when, for example, it is located on dark textiles. In such cases, further procedures need to be performed in order to visualize the pattern of GSR. Besides chemical procedures, an alternative light source or infrared photography can be utilized for non-destructive GSR visualization. In the work presented, these two techniques are compared based on shooting experiments using 26 different dark textiles. Within the range of the alternative light source, the use of a 440-nm light in combination with an orange-colored filter led to the best visualization of GSR in the form of fluorescent particles. Infrared photography, on the other hand, visualized GSR as dark particles, whereas—ideally—the dark textile reflected the infrared light and appeared bright. The comparison of both techniques revealed that the GSR distribution visualized by infrared photography was not identical to the GSR distribution visualized with 440-nm illumination in combination with an orange-colored filter. We concluded that infrared photography visualizes the inner powder soot zone, whereas illumination at 440 nm leads to fluorescence of the outer powder soot zone, which can be visualized using an orange-colored filter. Knowledge of this difference in visualization of the two powder soot zones is important for forensic practitioners assessing firing distances. In the literature, however, this difference is not noted as clearly.
KeywordsShooting distance Infrared photography Crime scene investigation Gunshot residue GSR Forensic light source Alternative light source
The authors wish to thank the Institute of Forensic Medicine, Cantonal Hospital, and the Department of Crime Scene Investigation, Cantonal Police, St. Gallen, Switzerland, for the realization of preliminary tests.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
- 1.Karger B (2004) Schussverletzungen. In: Brinkmann B, Madea B (eds) Handbuch gerichtliche Medizin. Springer, Berlin, pp 593–682Google Scholar
- 2.Pollak S (2015) Schussverletzungen. In: Madea B (ed) Rechtsmedizin, 3rd edn. Springer, Berlin Heidelberg, pp 245–262Google Scholar
- 3.Di Maio VJM (2016) Introduction to the classification of gunshot wounds. In: Di Maio VJM (ed) Gunshot wounds. Practical aspects of firearms, ballistics, and forensic techniques, 3rd edn. CRC Press, Boca Raton London New York, pp 57–108Google Scholar
- 6.Sellier K, Kneubuehl BP (2001) Wundballistik und ihre ballistischen Grundlagen, 2nd edn. Springer, BerlinGoogle Scholar
- 11.Marin N, Buszka J (2013) UV and narrowband visible light imaging. In: Miller LS (ed) Alternate light source imaging. Forensic photography techniques. Anderson Publishing Elsevier, Amsterdam, pp 25–61Google Scholar
- 12.Sellier K (1967) Schussentfernungsbestimmung. Verlag Max Schmidt-Römhild, LübeckGoogle Scholar
- 23.Marin N, Buszka J (2013) Electromagnetic radiation. In: Miller LS (ed) Alternate light source imaging. Forensic photography techniques. Anderson Publishing Elsevier, Amsterdam, pp 1–9Google Scholar
- 24.Davies A (2018) Ultraviolet fluorescence photography. In: Peres M (ed) Digital ultraviolet and infrared photography. Taylor and Francis, New York, pp 71–102Google Scholar
- 25.Trostle F (1988) Photographic examination of gunshot powder burn patterns through the use of infrared film. J Forensic Identif 38:57–61Google Scholar
- 29.Sterzik V, Bohnert M (2015) Bloodstain pattern analysis by infrared photography. In: 19th Nordic Congress on Forensic Medicine & 1st Annual Meeting of NAFT. S J F S, Stockholm, p 35Google Scholar
- 31.Redsicker DR (2001) Evidence documentation. In: The practical methodology of forensic photography, 2nd edn. CRC Press, Boca Raton, pp 199–242Google Scholar
- 33.Di Maio VJM (1999) Gunshot wounds, 2nd edn. CRC Press, New YorkGoogle Scholar