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Infrared Imaging as a Complementary Aid in Estimating Muzzle-to-Target Shooting Distance: An Application on Dark, Patterned and Bloody Sample

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The aim of this work was to assess the utility of the infrared camera as an effective tool for observing physical features like soot and gunshot residues around the entrance hole, to aid estimation of the shooting distances on bloody, dark and patterned samples.


In this study, white control samples, as well as colored and patterned fabrics were fired from several distances (contact, 6 inches, 12 inches, 24 inches, and 36 inches). All shootings were performed with three replicates. Post-shooting infrared images were taken by use of Crime-lite 82S infrared, before and after application of blood on the samples. Human whole blood was sprayed onto the clothing by means of an aerosol spray bottle in two stages, and was partially dried before capturing the image with the infrared camera. Using visual examination, it was not possible to detect any soot distribution on patterned fabrics, and the intensity of soot decreased and began to fade at 10 inches for other colored fabrics. The addition of blood to clothing masked the observation of iner soot and decreased the accuracy of the measurements. However, the soot was still visible when using an infrared camera on bloody samples, navy and black unknowns (10 inches) and patterned samples (contact and 6 inches), indicating the utility of an infrared camera on dirty and darker fabrics. The results of this study indicate that, similar to Modified Griess Test and Sodium Rhodizonate Test, soot alone is not the most accurate or reliable parameter for predicting true muzzle-to-target distance. However, an infrared camera enhanced the observation of presence of gunshot residues not easily visible to the naked eye on dark, patterned and bloody samples. Thus, the proposed application of infrared imaging can easily be utilized as a complementary approach in the prediction of muzzle-to-target firing distance on dark, patterned and bloody fabrics. (Publisher Abstract)