Study of backspatter using high-speed video of experimental gunshots

Abstract

Backspatter is biological material that is ejected from the entry wound against the line of fire. This phenomenon was also observed in wound ballistic simulations using so called "reference cubes" (12 cm edge length, 10% gelatin, 4 °C, paint pad beneath the cover). High-speed video records from 102 experimental shots to these target models using full metal jacketed bullets in the calibers .32 auto, .38 special, 9 mm Luger and .357 Magnum were analyzed for chronology, morphological appearance and velocity of fluid ejection. Generally, a short tail splashing of surface material occurred when the bullet was penetrating the target. In 51 shots from distance (≥ 5 cm), regardless of caliber and shot range, a linear jet of fluid started in connection with the first collapse of the temporary cavity. The initial velocity of the jet was measured between 6 and 45 m/s. The jet was streaming on for about 60 to 100 ms with a stochastic deviation of ± 13° to the horizontal. Close range and contact shots showed earlier and faster (up to 330 m/s) backspatter depending on the cartridge and the gap between muzzle and target. Gaseous aerosol-like spray and cone-like spatter indicated an increasing influence of muzzle gases with decreasing shot range. Even under standardized experimental conditions, variations of backspatter were observed in near/contact shots.

The muzzle to target distance —staining inside different parts of the firearm barrel

“…3 ). Previous research had demonstrated a linear ejection of fluid after shots from 5 cm distance and more [ 22 ]. If such a jet is meeting the muzzle of a gun, it depends on the movement of the gun, the muzzle-to-target distance and the velocity of the jet.…”

“…4 ) does not automatically lead to detectable staining in the posterior part of the barrel. The influence of muzzle gas pressure on the temporary cavity [ 21 ] and the ejection of fluid against the line of fire [ 22 ] has been demonstrated previously. The mechanism of staining in the depth of the firearm barrel, far from the muzzle remains yet unclear.…”

“…Further investigation was based on the endoscopic examination of firearm barrels [ 12 – 16 ], which confirmed the presence of biological staining in many, but not all firearm barrels after contact shot to the head. To understand the phenomenon and its variability, systematic experimental research was conducted [ 17 , 18 ] and a simple, but reliable target model [ 19 ] was developed which allowed for generating staining inside firearm barrels as well as observing the temporary cavity [ 20 , 21 ] and backspatter [ 22 ]. Other models, like a Synbone® polyurethane skull, were proposed [ 23 , 24 ].…”

Comparison of temporal cavity indicators when firing “FORT 12R” and “AE 790G1” into a non-biological body simulator

“…Due to the transparency and imitation of the physical characteristics of muscle and fat tissue, this material has become the most common. Also common practice is the use of time-lapse cameras, which allows recording processes lasting a fraction of a second [18] or combining gelatin with biological imitators of the human body [12]. At the same time, there are still ongoing discussions about the influence of various variables on the characteristics of gelatin, such as temperature factors, preparing features, etc.…”

Application of High-Speed Video Recording in Solving Scientific and Practical Problems of Forensic Ballistics

“…Высокоскоростная видеосъемка представляет интерес для различных видов экспертиз: судебно-баллистической, взрывотехнической, судебно-медицинской, инженерно-технической, трасологической. Например, она зарекомендовала себя в раневой баллистике при моделировании процессов воздействия поражающих элементов на биологические объекты [4][5][6], а также во взрывотехнике при изучении механизмов взрыва и разрушения материалов [7,8].…”