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

Biological traces inside firearm barrels were observed as a result of contact shots to the head. The present study was conducted to investigate the influence of the muzzle to target distance on staining inside the anterior and posterior part of firearm barrels. Ninety-nine shots were fired to so-called reference cubes (10% gelatine, 12 cm edge length, embedded paint-blood-pad) using three current handguns. Shot range was varied from contact to 50 cm distance. High-speed cameras recorded external backspatter. Endoscopic examination assessed visible staining along the barrel. Each two swabbings were gathered from the anterior and the posterior part of the barrel. The first swabs were submitted to quantitative PCR, the second ones to DNA-RNA-co-extraction. Thorough mechanical and chemical cleaning was performed to avoid any contamination which was controlled by negative zero swabs after each cleaning. In single shots up to 50 cm distance, minimal, but DNA-positive sporadic traces were detected inside the barrel in vicinity of the muzzle. Visible complex staining varying in extent was observed in the anterior barrel part for 10 cm or less distance in dependence of the calibre. The posterior part showed detectable traces only after close range shots (< 5 cm). Generally staining inside the barrel decreased from the muzzle to the rear end, which correlated with the yield of DNA. Some contact shots did not cause any staining in the posterior part of the barrel despite massive external backspatter. Blood-specific miRNA was primarily found where DNA was detected. This experience encourages to take a second swab for RNA analysis. The amount of nucleic acids in the barrel at varying muzzle to target distances is subject to large variations between individual shots and therefore appears not suitable for a reliable determination of the shot distance in a particular case on its own. Instead, shot range estimation should also take into account morphology and distribution of traces inside the barrel.

As above, so below: Deposition, modification, and reutilization of human remains at Marmoles cave (Cueva de los Marmoles: Southern Spain, 4000-1000 cal. BCE).

The deposition and manipulation of human remains in natural caves are well known for the Neolithic of Southern Iberia. The cultural meaning of these practices is however still largely unclear. Cueva de los Marmoles (CM, Priego-Córdoba) is one of the most important cave contexts from Southern Spain, which returned a large number of commingled skeletal remains suggesting its funerary use from the Neolithic to the Late Bronze Age. Here we discuss CM from a chronological and cultural perspective based on new radiocarbon, anthropological, and taphonomic analyses. These include the estimation of the minimum number of individuals, the exploration of fragmentation patterns characterizing different skeletal regions, and the macroscopic and microscopic analysis of modifications to the remains of possible anthropic origin. Radiocarbon data point to a funerary use of CM between the 5th -2nd millennium cal. BCE. MNI estimates reveal the presence of at least 12 individuals (seven adults and five nonadults). The low representation of elements from hands and feet suggests that individuals were placed in the cave while partially decomposed. Anthropic traces on the remains (e.g. fresh fractures, marrow canal modifications, and scraping marks) hint at their intentional fragmentation, cleaning from residual soft tissues, and in some cases reutilization. These practices are well-exemplified by the recovery of one "skull cup" and of two long bones used as tools. These data align with those from other cave contexts from the same geographic region, suggesting the presence, especially during the Neolithic period, of shared ideologies centered on the human body.

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

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.

The reference cube: A new ballistic model to generate staining in firearm barrels.

After contact shots to the head biological traces can be found inside firearm barrels. So far silicone coated, gelatin filled box models were used to generate such staining according to the triple contrast method (mixture of acrylic paint, barium sulfate and blood sealed in a thin foil bag). This study was conducted to develop a transparent ballistic model allowing contact shots. Gelatin filled polyethylene bottles with and without a silicone coat were tested in comparison to non-covered gelatin blocks. Finally, thin foil bags of 5 cm × 5 cm dimension were glued on a synthetic absorbent kitchen wipe on top of which 1 L 10% gelatin solution was molded to create blocks of 8.5 cm length. A kitchen wipe with a paint pad on its inside formed the front of the cube. Three contact shots each with a 9 mm Luger pistol and a .38 special revolver were performed on all model variations. The staining was documented by endoscopy and swabs gathered from both ends of the barrel were analyzed by quantitative PCR. Reliable staining was achieved using the front covered gelatin block with comparable results to the silicone coated box model used before. For further research using ballistic models to simulate a human head a symmetric form of the gelatin block such as a cube is recommended.