Backspatter from experimental close-range shots to the head. II. Microbackspatter and the morphology of bloodstains.

Backspatter is the ejection of biological material from a gunshot entrance wound against the line of fire. Backspatter of blood was investigated experimentally in transverse gunshots to the heads of calves (n = 9) from shooting distances of 0-10 cm. The resulting bloodstains were documented on white paper placed horizontally 60 cm below the impact site. The morphology of bloodstains and the distribution of microstains (diameter < 0.5 mm) is reported. The number of microbackspatter stains per gunshot varied between 39 and 262 and the maximum travelling distance was 69 cm while the vast majority of micro-droplets accumulated between 0 and 40 cm. The direction a single droplet can take comprises every possible angle between the most tangential ones to the skin surface. Microstains exclusively were circular to slightly oval. The morphology of macrobackspatter stains (diameter > 0.5 mm) varied from round to elongated with circular, drop-like and stains in the form of exclamation marks predominating. Small macrostains (0.5-4 mm) made up more than 90% of the macrostains and no systematic relationship between distance travelled and size of the stains could be established. The necessity of appropriate lighting and magnification in the investigation of surfaces for backspatter is stressed because many microstains are located in the proximity of the entrance wound where the firearm and the shooting hand are located in cases of close-range shots.