Skin simulants for wound ballistic investigation - an experimental study.

Gunshot wound analysis is an important part of medicolegal practice, in both autopsies and examinations of living persons. Well-established and studied simulants exist that exhibit both physical and biomechanical properties of soft-tissues and bones. Current research literature on ballistic wounds focuses on the biomechanical properties of skin simulants. In our extensive experimental study, we tested numerous synthetic and natural materials, regarding their macromorphological bullet impact characteristics, and compared these data with those from real bullet injuries gathered from medicolegal practice. Over thirty varieties of potential skin simulants were shot perpendicularly, and at 45°, at a distance of 10 m and 0.3 m, using full metal jacket (FMJ) projectiles (9 × 19 mm Luger). Simulants included ballistic gelatine at various concentrations, dental silicones with several degrees of hardness, alginates, latex, chamois leather, suture trainers for medical training purposes and various material compound models. In addition to complying to the general requirements for a synthetic simulant, results obtained from dental silicones shore hardness 70 (backed with 20 % by mass gelatine), were especially highly comparable to gunshot entry wounds in skin from real cases. Based on these results, particularly focusing on the macroscopically detectable criteria, we can strongly recommend dental silicone shore hardness 70 as a skin simulant for wound ballistics examinations.

Bursting of the upper jaw prosthesis and fractures of the lower jaw as indirect injury pattern caused by a headshot: a case report.

Gunshots to the human body can cause direct and indirect injuries. Direct injuries are a consequence of the projectile guiding its way through the body, creating a permanent wound channel and thereby damaging the penetrated as well as the adjacent tissue. In addition, the temporary wound cavity is responsible for indirect injuries occurring distant to the actual wound tract. This can potentially affect different types of tissue, like blood vessels, organs, or bones, that are not directly passed through by the projectile. For this case report, we describe a suicidal headshot to the temporal area where the extension of the temporary wound cavity and its subsequent collapse led to massive energy transfer to the surrounding tissue leading to breakage of the upper dental prosthesis and fractures of the lower jaw. Thereby outlining the ballistic mechanisms causing indirect injury pattern that have to be considered when examining gunshot wounds.

Gunshot residues found at the exit wound: a case report.

Gunshot residues (GSRs) play an important role in forensic investigations of gun-related violence. The presence of GSRs has been described to help to identify the bullet entry area, as it was supposed not to be found at exit wounds. This report details the suicidal headshot of an 84-year-old male where unburned tube-like, cuboid and flake-formed powder particles have been found not only at the inside of the muzzle but also circular around the exit wound. With very short-barrelled weapons, it must be expected that part of the propellant charge leaves the barrel unburned behind the bullet. In contrast to that, the barrel length of the used weapon should lead to a complete burn-up of powder particles. The surprisingly large number of unburned powder particles present at the exit wound of the injury gave reason for further investigation to understand the underlying ballistic aspects and outlines the importance of having a close look at incidence scene photos during an investigation.

Skin laceration caused by a short distance shot from a pepper spray launcher: a case report.

Pepper spray launchers are more precise and wind stable compared to conventional pepper sprays and are commonly used as a self-defensive tool. With the advanced potential, they may also harbour a greater risk for injuries, especially if they are not used within the suggested safety distance. If the shooting distance is below 1.5 m, energy densities may exceed the threshold energy density for the penetration of skin leading to skin laceration. We present a case where a man is hit by the liquid jet of a JPX Jet Protector® with an estimated shooting distance of 0.3 m. The man suffered from a bleeding skin laceration, which had to be sewed in the hospital. This case report furthermore outlines the potentially dangerous effect of pepper spray launchers and thereby their role in forensic investigations.

Deadly injuries through recoilless anti-tank weapons while military shooting practice-two case studies from Germany and Switzerland.

In this casuistry, two accidents from Germany and Switzerland are presented that happened during the shot of recoilless anti-tank weapons. In both cases, the injuries led to the death of two soldiers: A 22-year-old soldier in Germany was struck by the counter mass of a so-called Davis gun which had been fired by a comrade during a firing exercise; he died from his severe injuries, especially in the abdominal part of the body. As a peculiarity of the wound morphology, it was found to be a thick-layered, metallic, gray material in the wound cavity, which corresponded to the material of the counter mass that was ejected opposite to the shooting direction. The other case took place in Switzerland, where a 24-year-old soldier was seriously injured during an exercise with portable anti-tank rockets. At the time the shot was fired, he stood behind the launcher and was hit by the propulsion jet of the rocket motor. He died as well from his severe injuries, which were located at the chest done by the gas jet and by the very high pressure. In both cases, two different causes of death were present: massive blunt violence in the first case versus a jet of hot gases of very high speed and temperature in the second case.

Threshold of the skull injury for blunt force impacts under free and constraint boundary conditions.

The formation of skull fractures is an important topic in legal medicine. In particular, the influence of boundary conditions is controversially discussed in the literature. A study focusing solely on this aspect was missing. This study aimed to investigate the influence of boundary conditions on the energy threshold for head fractures. Because of the great variability of biological tissue of real skulls, we opted for a head model made from a polyurethane sphere filled with gelatin. Furthermore, we decided to investigate two opposite situations: A fixed configuration where a model was placed on a rigid surface and a (quasi) free boundary configuration where the head model was held at a force of 5 N compensating for gravity. For both configurations, we determined the acceleration signal of the impactor, the force, and the energy threshold for head fracture. It turned out that the fracture forces for both configurations were the same whereas the energy threshold was 11.0 J for the fixed and 13.6 J for the free boundary. The difference seems to be negligible if compared to the effect of varying structural mechanical properties of real human heads. This means that in a forensic case, the two situations most probably cannot be distinguished. To investigate the influence of the impactor mass, we developed a mathematical model and fitted the experimental data. As a result, we found that in the free configuration, a larger mass increases the energy threshold for head fracture. So that in principle, the two configurations are distinguishable.

Influence of a soft tissue layer covering the kidney upon blunt impact.

Blunt abdominal organ injury is an abundant and relevant topic in forensic medicine, yet comparatively few experimental studies have been performed to quantify organ injury threshold parameters. The goal of this study was to relate an impact to a kidney injury determining an energy threshold while taking account of the influence of the overlaying soft tissue thickness. A model consisting of ballistic gelatin with an embedded filled porcine kidney was made such that a gelatin layer of 2 or 4 cm thickness covered the organ. An impactor was dropped on this model from different heights and the resulting organ damage was categorized according to the abbreviated injury scale (AIS). The 50% energy threshold for damage and the 50% energy threshold causing injuries ≥ AIS 3 were determined for the two protecting soft layers to be 22 J and 32 J and 27 J and 36 J, respectively. A finite element model was created to determine the strain energy densities at the depth of the organ's surface for these energies. The strain energy densities for the 50% damage thresholds were 88.9 mJ/cm3 and 86.7 mJ/cm3 for 2 and 4 cm and for the injuries ≥ AIS 3104.2 mJ/cm3 and 98.7 mJ/cm3. For forensic cases, this means that the thickness of the abdominal layers must be taken into account when the severity of an injury is used to draw conclusions about the applied impact strength.

Impact energy of everyday items used for assault.

Blunt force is a frequently used type of violence especially because it can be performed with basically every object of our daily lives or with bare hands or feet. The injuries and medical consequences have been widely examined, whereas the forces and especially the energies acting on impact have rarely been analyzed. The aim of the present study is to provide the impact energy and its ranges of four longish everyday items with different characteristics for male and female offenders. Additionally, the moment of inertia (MOI) for all the objects was calculated and its influence on the energy determined. A combination wrench, aluminum pipe, golf club, and spade were chosen as representatives of the four categories short, medium length with the center of mass (COM) in the middle, medium length with the COM close to the hitting point, and long and heavy. A total of 880 strikes have been performed by 11 volunteers. The results show the mean energy values of wrench, pipe, golf club, and spade for men of 51.1, 74.4, 93.5, and 166.7 J. For women, the results are 33.0, 41.0, 56.5, and 76.8 J. Knowing the energy thresholds for certain fractures and injuries, these results help to assess whether a claimed hit may have caused the fracture or injury or not.

Assessment of a specifically developed bullet casing gun for the stunning of water buffaloes.

Water buffaloes and cattle differ considerably with respect to the anatomy of the head. As a result, captive bolt stunners often fail to reliably produce adequate loss of consciousness in water buffaloes and, thus, do not fulfill animal welfare requirements. The goal of the present study was to assess and validate a new stunning device for water buffaloes meeting animal welfare and occupational safety requirements. The newly designed bullet casing gun uses .357Mag/10.2g hollow point bullets and has additional safety features. Its effectiveness and usability were assessed under practical conditions in an abattoir as based on widely accepted criteria. Stunning resulted in deep unconsciousness in 19 out of 20 water buffaloes. One 9-year old male did not immediately collapse. Except for very old bulls, the device presented herewith provides a means to stun water buffaloes of both sexes effectively and reliably while keeping occupational hazards to a minimum.

Energy loss and impact of various stunning devices used for the slaughtering of water buffaloes.

Stock management of the Swiss water buffalo livestock results in the slaughtering of about 350 animals per year. As the stunning of water buffaloes still is an unresolved issue, we investigated the terminal ballistics of currently used perforating stunning devices. Cartridge fired captive bolt devices, handguns and a bullet casing gun were tested in a shooting steep by firing on bisected heads, forehead plates and soap blocks. Energy loss of captive bolts confirmed their inadequacy when used for heavy water buffaloes, notably adult males. As for the free projectiles, ballistics revealed that beyond the impact energy, bullet deformation has a strong impact on the outcome. Light 9mm Luger or .38 Spl bullets as well as large deformable .44 Rem. Magnum bullets should be avoided in favor of heavier .357 Magnum deformation ammunition. These data have been translated into the development of a new stunning device for water buffaloes meeting both animal welfare and occupational safety requirements.

Stabbing energy and force required for pocket-knives to pierce ribs.

PURPOSE: In addition to reconstructing the course of events, the medical examiner will often have to answer questions regarding the force necessary to inflict a certain injury in stabbing incidents. Several groups have examined the force needed to penetrate soft-tissue and clothing; however, no studies addressing the energy needed for penetrating ribs exist. Therefore, we decided to investigate this force on an animal model. METHOD: Ribs from healthy, 8 to 10-month-old pigs were used as a substitute for human ribs. These ribs were then stabbed either transversely or longitudinally with two different pocket-knife blades, namely a Swiss Army pocket knife and a sturdier pocket knife (Classic Schnitzmesser, Herbertz Solingen) dropped from a drop-tower at defined heights and therefore defined energies. RESULTS: Longitudinally orientated stabs showed complete piercing of the ribs at approximately 11 Joules (J) or with a stabbing force in excess of 906 Newton (N) for both blade types. Transversely orientated stabs, however, displayed complete piercing between 11 and 16 J, or in excess of 1198 N, with the sturdy pocket knife tending to require a little more energy than the Swiss army pocket knife. CONCLUSIONS: Young adult porcine ribs are completely pierced by pocket knife blades at energies between 11 and 16 J. Assuming the porcine ribs are comparable to those ribs of young adult humans, our results indicate that a complete penetration of the chest wall through the ribs by stabbing with a pocket knife is rather easily achieved.

A patterned abrasion caused by the impact of a cartridge case may simulate an atypical muzzle imprint mark.

In contact shots, the muzzle imprint is an informative finding associated with the entrance wound. It typically mirrors the constructional components being in line with the muzzle or just behind. Under special conditions, other patterned skin marks located near a gunshot entrance wound may give the impression to be part of the muzzle imprint. A potential mechanism causing a patterned pressure abrasion in close proximity to the bullet entrance site is demonstrated on the basis of a suicidal shot to the temple. The skin lesion in question appeared as a ring-shaped excoriation with a diameter corresponding to that of the cartridge case. Two hypotheses concerning the causative mechanism were investigated by test shots: - After being ejected, the cartridge case ricocheted inside a confined space (car cabin in the particular case) and secondarily hit the skin near the gunshot entrance wound. - The ejection of the cartridge case failed so that the case became stuck in the ejection port and its mouth contacted the skin when the body collapsed after being hit.

Magnetic resonance imaging and computer tomography of brain lesions in water buffaloes and cattle stunned with handguns or captive bolts.

Owing to the demand for genuine mozzarella, some 330 water buffaloes are being slaughtered every year in Switzerland albeit a stunning procedure meeting animal welfare and occupational safety requirements remains to be established. To provide a basis for improvements, we sized anatomical specifics in water buffaloes and cattle and we assessed brain lesions after stunning with captive bolts or handguns by diagnostic imaging. In water buffaloes and cattle, the median distance from the frontal skin surface to the inner bone table was 74.0mm (56.0-100.0mm) vs 36.6mm (29.3-44.3mm) and from skin to the thalamus 144.8mm (117.1-172.0mm) vs 102.0 (101.0-121.0mm), respectively. Consequently, customary captive bolt stunners may be inadequate. Free bullets are potentially suitable for stunning buffaloes but involve occupational safety hazards. The results of the present study shall be used to develop a device allowing effective and safe stunning of water buffaloes.

The influence of striking object characteristics on the impact energy.

A common form of violence investigated in legal medicine is blunt trauma caused by striking with different objects. The injuries and medical consequences have been widely examined, whereas the forces and especially the energies acting on impact have rarely been analyzed. This study focuses on how the impact energy of different striking objects depends on their characteristics. A total of 1170 measurements of horizontal strikes against a static and relatively heavy pendulum have been acquired with 13 volunteers. The main focus was laid on how the weight, the length, and the center of mass of the different striking objects influenced the striking energy. The results show average impact energies in the range of 67.3 up to 311.5 J for men with an optimum weight of about 1.3 kg with its center of mass in the far end quarter for a 1-m-long striking object. The average values for women range from 30 to 202.6 J, with an optimum weight between 1.65 and 2.2 kg and similar settings for the center of mass as the men. Also, the impact energies are getting higher with shorter object lengths and reach a maximum at a length of about 0.3 to 0.4 m. The male volunteers' impact energy was on average by 84.2% higher than the values of the female volunteers, where the impact masses were very similar and the impact velocities played the key role.

Fatal contact shot to the chest caused by the gas jet from a muzzle-loading pistol discharging only black powder and no bullet: case study and experimental simulation of the wounding effect.

In modern medico-legal literature, only a small number of publications deal with fatal injuries from black powder guns. Most of them focus on the morphological features such as intense soot soiling, blast tattooing and burn effects in close-range shots or describe the wound ballistics of spherical lead bullets. Another kind of "unusual" and potentially lethal weapons are handguns destined for firing only blank cartridges such as starter and alarm pistols. The dangerousness of these guns is restricted to very close and contact range shots and results from the gas jet produced by the deflagration of the propellant. The present paper reports on a suicide committed with a muzzle-loading percussion pistol cal. 45. An unusually large stellate entrance wound was located in the precordial region, accompanied by an imprint mark from the ramrod and a faint greenish discoloration (apparently due to the formation of sulfhemoglobin). Autopsy revealed an oversized powder cavity, multiple fractures of the anterior thoracic wall as well as ruptures of the heart, the aorta, the left hepatic lobe and the diaphragm. In total, the zone of mechanical destruction had a diameter of approx. 15 cm. As there was no exit wound and no bullet lodged in the body, the injury was caused exclusively by the inrushing combustion gases of the propellant (black powder) comparable with the gas jet of a blank cartridge gun. In contact shots to ballistic gelatine using the suicide's pistol loaded with black powder but no projectile, the formation of a nearly spherical cavity could be demonstrated by means of a high-speed camera. The extent of the temporary cavity after firing with 5 g of black powder roughly corresponded to the zone of destruction found in the suicide's body.

Added value of dual-energy computed tomography versus single-energy computed tomography in assessing ferromagnetic properties of ballistic projectiles: implications for magnetic resonance imaging of gunshot victims.

OBJECTIVE: The objective of this study was to assess the discriminative power of dual-energy computed tomography (DECT) versus single-energy CT (SECT) to distinguish between ferromagnetic and non-ferromagnetic ballistic projectiles to improve safety regarding magnetic resonance (MR) imaging studies in patients with retained projectiles. MATERIALS AND METHODS: Twenty-seven ballistic projectiles including 25 bullets (diameter, 3-15 mm) and 2 shotgun pellets (2 mm each) were examined in an anthropomorphic chest phantom using 128-section dual-source CT. Data acquisition was performed with tube voltages set at 80, 100, 120, and 140 kV(p). Two readers independently assessed CT numbers of the projectile's core on images reconstructed with an extended CT scale. Dual-energy indices (DEIs) were calculated from both 80-/140-kV(p) and 100-/140-kV(p) pairs; receiver operating characteristics curves were fitted to assess ferromagnetic properties by means of CT numbers and DEI. RESULTS: Nine (33%) of the projectiles were ferromagnetic; 18 were nonferromagnetic (67%). Interreader and intrareader correlations of CT number measurements were excellent (intraclass correlation coefficients, >0.906; P<0.001). The DEI calculated from both 80/140 and 100/140 kV(p) were significantly (P<0.05) different between the ferromagnetic and non-ferromagnetic projectiles. The area under the curve (AUC) was 0.75 and 0.8 for the tube voltage pairs of 80/140 and 100/140 kV(p) (P<0.05; 95% confidence interval, 0.57-0.94 and 0.62-0.97, respectively) to differentiate between the ferromagnetic and non-ferromagnetic ballistic projectiles; which increased to 0.83 and 0.85 when shotgun pellets were excluded from the analysis. The AUC for SECT was 0.69 and 0.73 (80 and 100 kV[p], respectively). CONCLUSIONS: Measurements of DECT combined with an extended CT scale allow for the discrimination of projectiles with non-ferromagnetic from those with ferromagnetic properties in an anthropomorphic chest phantom with a higher AUC compared with SECT. This study indicates that DECT may have the potential to contribute to MR safety and allow for MR imaging of patients with retained projectiles. However, further studies are necessary before this concept may be used to triage clinical patients before MR.

The varying size of exit wounds from center-fire rifles as a consequence of the temporary cavity.

To study the question whether and how the size and position of the temporary cavity influence the morphology and especially the size of a bullet exit wound, test shots were fired to composite models consisting of gelatine and pig soft tissue covered with skin (at the exit site). The dimensions of the composite model were determined such that the exit planes were located either at the level of the narrow channel or within the temporary cavity or behind it. The chronological sequence of wound formation and its relation to the current position of the bullet were documented by means of a high-speed camera. Test shots were fired from a distance of 10 m using 5.56 × 45 mm cartridges with full metal-jacketed pointed bullets (v 0 ∼ 912 m/s, E 0 ∼ 1,663 J). The study proved that the extension and position of the temporary wound cavity was decisive for the size of the exit wound: An exit plane within the cavity resulted in particularly large skin lesions, whereas the wound diameters were much smaller if the exit plane was located in front or behind the cavity. The exit hole reaches its maximum size only after the bullet has left the target synchronous to the staggered expansion of the temporary cavity.

Lung injury similar to blast lung in a case of shotgun wound of the head.

Primary blast lung injury after explosions has been well described in the literature. A case of injury to the lung, after a shotgun wound to the head, similar to primary blast lung, is presented. Histological appearances of the lung revealed alveolar over distension, rupture and intra-alveolar hemorrhage. Primary blast lung injury is considered the reserve of high-order explosives; however, this case reveals similar injuries from a shotgun (low-order explosive), which has not been reported before to the best of our knowledge.

Maximum flight velocity of blood drops in analysing blood traces.

When analysing blood spatters, traces often occur which regarding the collision angle, cannot be allocated to any supposed centre of origin. Drops following highly curved (ballistic) trajectories usually form these types of traces. The reconstruction of such trajectories requires knowledge of the mass, the diameter (of which approximations are known) and the velocity of the blood drops. This article provides an upper range of the velocity in relation to the diameter of the blood drops based on physical laws. This is very helpful in analysing ballistic trajectories.

Collateral damage--penetrating head injury and orbital injury: a case report.

We report a case of an accidental death or potential suicide by revolver with subsequent injury of another person. A 44-year-old man shot himself in the head while manipulating his .38 caliber special revolver in the kitchen in the presence of his wife, standing approximately 1.5 m next to him. After passing through the husband's head, the lead round-nose bullet entered the region underneath his wife's left eye. When the bullet left the man's head, it retained the energy to penetrate the soft tissue at this distance, including the skin and thin bone plates like the orbital wall. Owing to the low energy of the projectile, the entry wound was of atypical in shape and without loss of tissue. Only a small line--resembling a cut--was externally visible. The man died in the hospital from his injuries; his wife suffered visual loss of her left eye.