Abstract
After contact shots to the head, biological traces can be found inside the barrel of the firearm. Experimental protocols to generate this sort of staining, using 12 cm gelatin cubes containing thin foil bags filled with acrylic paint, human blood, and radiocontrast agent, have been developed. Previous research on shots fired at a distance has shown the underlay sustaining these gelatin cubes has an influence on experimental results. This study was conducted to investigate the role of the sustaining base of the gelatin blocks during contact shots, and its influence on the staining result inside firearm barrels. Eighteen contact shots were performed using 22 LR, 32 ACP (7.65 Browning) and 9 mm Luger semi-automatic pistols. With each pistol, shots were fired onto six gelatin cubes; three placed upon a rigid platform and three upon an elastic underlay. The shots were recorded by a high-speed video camera as they penetrated the gelatin cube. Any staining present inside the firearm barrels after the shots were fired was documented by endoscopy. Cross sections of the gelatin blocks were then compared to the high-speed video. It was found that the nature of the staining inside the barrel was not influenced by the underlay sustaining the target model. In the experiment using a 9 mm Luger, the rigid counterfort provoked a visible distortion of the temporary cavity, but, cross sectional analysis of the gelatin cubes did not reveal a relevant influence of the sustaining underlay on the crack length in the gelatin. This could be explained by a secondary expansion of the temporary cavity left by the projectile as a consequence of subsequent inflow of muzzle gases.
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Acknowledgments
The expert technical assistance of Nicole Schwendener (Bern) is gratefully acknowledged.
Funding
This research work was funded by the SNF (Swiss National Science Foundation, project 310030E-147628 / 1).
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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
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Electronic supplementary material
Online Resource 1
Endoscopic view of the posterior barrel part of the .22 LR pistol showing abundant staining up to the chamber. (GIF 136 kb)
Online Resource 2
Maximum TC in the reference cube placed on a sponge after a contact shot using the .22 LR HV non-deforming cartridge. (GIF 58 kb)
Online Resource 3
Endoscopic view of the barrel of the pistol cal. 9 mm Luger showing extended spray-like staining from the muzzle to the posterior half of the barrel. (GIF 175 kb)
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Schyma, C., Müller, R., Brenčičová, E. et al. Distortion of the temporary cavity and its influence on staining in firearm barrels. Forensic Sci Med Pathol 14, 202–208 (2018). https://doi.org/10.1007/s12024-018-9971-0
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DOI: https://doi.org/10.1007/s12024-018-9971-0