Distortion of the temporary cavity and its influence on staining in firearm barrels

  • Christian Schyma
  • Rolf Müller
  • Eva Brenčičová
  • Julia Brünig
Original Article

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.

Keywords

Suicide Firearm barrel Wound ballistics Backspatter Biological traces Muzzle gases 

Notes

Acknowledgments

The expert technical assistance of Nicole Schwendener (Bern) is gratefully acknowledged.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interests.

Ethical approval

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.

Informed consent

Informed consent was obtained from all individual participants included in the study.

Supplementary material

12024_2018_9971_Fig7_ESM.gif (137 kb)
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)

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High resolution image (TIFF 4112 kb)
12024_2018_9971_Fig8_ESM.gif (58 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)

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High resolution image (TIFF 1480 kb)
12024_2018_9971_Fig9_ESM.gif (175 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)

12024_2018_9971_MOESM3_ESM.tif (4 mb)
High resolution image (TIFF 4112 kb)

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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Institute of Forensic MedicineUniversity of BernBernSwitzerland
  2. 2.Criminal Investigation Service of the Cantonal Police Department of BernBernSwitzerland

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