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.
Highlights
Wound ballistics investigates the interaction of projectile and tissue
The present study investigates back spattered fluid in the context of experimental gunshots to the 12 x 12x12 c m3 gelatin reference cube
A point zero in time has to be defined. Whereas it is obvious for shots from distance that this point is the moment when the bullet penetrates into the target model, the situation is different for contact or near contact shots
Summary
Wound ballistics investigates the interaction of projectile and tissue. If the energy density of a bullet is larger than the tissue specific value, the bullet penetrates [1]. Such a non-elastic impact of a bullet on a biological target leads to the tissue being crushed [2, 3]. During the experimental investigation of staining inside firearm barrels [9], transparent target models (“reference cube” [10]) were introduced. The reference cube was originally designed to create optically visible traces in gun barrels, it was possible to observe the propagation of colored material in and against the direction of fire. The observed properties of the target model can contribute to a more comprehensive understanding of “backspatter”
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