The influence of muzzle gas on the temporary cavity

The influence of a skin simulant on bullet trajectory deflection in ballistic gelatine

This study explored the influence of a skin simulant on the trajectory deflection of bullets fired through gelatine blocks. Full metal jacket round nose (FMJ-RN) bullets in caliber 9 mm Luger were fired through gelatine blocks that were clad with a skin simulant at the front, at the back and both at the front and back. The angle between the bullet trajectories before and behind the blocks were calculated for each shot. This angle is a measure for bullet trajectory deflection. The ballistic resistance of the used skin simulant was defined as the threshold value in J/mm2 where 50 % of all fired projectiles are expected to perforate. This value varied between 0.22 and 0.29 J/mm2 for the skin simulant samples that were used. These values are higher than most values found in the literature for human skin, which vary between 0.12 J/mm2 and 0.26 J/mm2. The deflection results recorded with a skin simulant at the front, at the back and both at the front and back were compared to each other and to a dataset from similar bullets, fired through similar gelatine blocks without a skin simulant. Despite the fact that the ballistic resistance of the chosen skin simulant was relatively high, trajectory deflection was not influenced significantly by its presence for all tested conditions.

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.

A modified chain-based sponge dressing controls junctional hemorrhage in the tactical combat casualty care simulation of pigs

BACKGROUND

Hemorrhage has always been the focus of battlefield and pre-hospitalization treatment. With the increasing fatality rates associated with junctional bleeding, treatment of bleeding at junctional sites has gradually gained attention in battlefield trauma emergency care. We designed a modified chain-based sponge dressing with a medical polyvinyl alcohol sponge that can be used to treat junctional hemorrhage and tested its hemostatic efficacy and biocompatibility.

METHODS

Twenty adult Bama miniature pigs were randomly divided into the modified chain-based sponge dressing (MCSD) and standard gauze (SG) groups. The right femoral artery of the pigs was shot at after anesthesia. The Bama miniature pigs were moved to the safety zone immediately to assess the condition according to the MARCH strategy, which evaluates massive hemorrhaging, airway obstruction, respiratory status, circulatory status, head injury & hypothermia. Hemoglobin and coagulation status were checked during the experiment.Among the pigs in which the inguinal hemorrhagic model based on bullet penetrating wounds was successfully established, those in the MCSD group received a disinfected MCSD for hemostasis, while those in the SG group received standard gauze in an imbricate manner to pack the bullet exit and entrance wounds to stop bleeding until the wound was filled, followed by compression for 3 min at sufficient pressure. CT scanning, transmission electron microscopy, and HE staining were conducted after experiment.

RESULTS

The MCSD group showed lower hemostasis time and blood loss than the gauze group. The MCSD group also showed a higher success rate of treatment,more stable vital signs and hemoglobin level. The CT scanning results showed tighter packing without large gaps in the MCSD group. The histopathological assessments and the transmission electron microscopy and HE staining findings indicated good biocompatibility of the polyvinyl alcohol sponge.

CONCLUSION

The MCSD met the battlefield's requirements of speedy hemostasis and biosafety for junctional hemorrhage in Bama miniature pigs. Moreover, in comparison with the conventional approach for hemostasis, it showed more stable performance for deep wound hemostasis. These findings provide the theoretical and experimental basis for the application of MCSD in the treatment of hemorrhage in the battlefield in the future.

Ten years of molecular ballistics-a review and a field guide

Molecular ballistics combines molecular biological, forensic ballistic, and wound ballistic insights and approaches in the description, collection, objective investigation, and contextualization of the complex patterns of biological evidence that are generated by gunshots at biological targets. Setting out in 2010 with two seminal publications proving the principle that DNA from backspatter collected from inside surfaces of firearms can be retreived and successfully be analyzed, molecular ballistics covered a lot of ground until today. In this review, 10 years later, we begin with a comprehensive description and brief history of the field and lay out its intersections with other forensic disciplines like wound ballistics, forensic molecular biology, blood pattern analysis, and crime scene investigation. In an application guide section, we aim to raise consciousness to backspatter traces and the inside surfaces of firearms as sources of forensic evidence. Covering crime scene practical as well as forensic genetic aspects, we introduce operational requirements and lay out possible procedures, including forensic RNA analysis, when searching for, collecting, analyzing, and contextualizing such trace material. We discuss the intricacies and rationales of ballistic model building, employing different tissue, skin, and bone simulants and the advantages of the “triple-contrast” method in molecular ballistics and give advice on how to stage experimental shootings in molecular ballistic research. Finally, we take a look at future applications and prospects of molecular ballistics.

Study of backspatter using high-speed video of experimental gunshots

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.

A distant relationship?-investigation of correlations between DNA isolated from backspatter traces recovered from firearms, wound profile characteristics, and shooting distance

In molecular ballistics, where traces originating from the use of firearms against biological targets are investigated, "backspatter" traces are of particular importance. This biological material comprising blood and tissue from the victim is propelled back from the bullet entry site towards the direction of the shooter and can consolidate and persist on the inner and outer surfaces of the firearm, from where it can be collected and analyzed. Thus, a connection between the weapon and the victim can be established solely by molecular biological trace analysis. For the criminalistic investigation of gun-related crimes, the determination of the distance between the weapon and the victim can be of critical importance in reconstructing the circumstances of a crime. In this study, we investigated possible correlations between the shooting distance and the amount of backspatter in/on the used firearm. To this purpose, we employed a previously established skull model and performed shootings in triplicates from various distances up to 50 cm with two types of handguns (pistol and revolver). Backspatter was collected from various sampling locations, and DNA contents were quantified. A post-shooting wound channel evaluation was conducted by optical and radiological evaluation. The obtained DNA yields varied considerably between replicates from the same and from different distances. In contrast, apart from contact shots, no meaningful differences were observable in wound channel evaluations. In summary, no meaningful correlation between backspatter distribution and DNA yields, the shooting distance and the condition of the wound channel could be established.