The cutting edge-an investigation into the pressure necessary for cutting skin with different knife blade types.

Sharp force trauma is routinely encountered in forensic practice. Often the question is posed, how much pressure or energy would have been necessary to inflict a cut with a specific knife, in order to further characterize the perpetrator or determine his intent to cause harm. This paper investigates two knife blades and its individual pressures needed to cut through the epidermis and dermis. In order to examine the necessary force for cutting through the skin, we performed experiments on a piglet skin-on-gelatin phantom. Two similarly small knives-a paring knife with a serrated blade and a Swiss Army pocket knife with a smooth blade-were moved over the phantom surface using a mobile cutting apparatus with varying weight on the load arm with the knife. The depth of the cut was to be determined according to a scale from zero to three: grade 0 = no cut; grade 1 = cut into epidermis only; grade 2 = cut into dermis; grade 3 = complete transection of the entire skin. Each cut inflicted at a specific pressure force was assessed closely in order to ascertain depth, calculate the velocity, and ultimately determine the point at which a cut would inflict grade 3 damage. The smooth blade of a pocket knife needed at least 1900g pressure in order to slice through pig skin mounted on a thick gelatin block, whereas a serrated blade of a paring knife managed to cut into or through the dermis at a comparatively lower force of 700g. Our study shows that at the same cutting velocity, a significant difference in pressure is necessary to inflict the same degree of damage.

Penetration Depths of Conducted Electrical Weapon Probes Into Human Skull Phantoms.

Occasional case reports have described isolated cases of conducted electrical weapon (CEW) probes piercing the human skull. In an experimental setting, we examined whether these cases were just unfortunate incidents, how deeply such probes can pierce the skull, and whether firing distance and CEW probe type play a role in the skull-piercing capability.We fired 5 different CEW cartridges (XP 10.6 m, XP 7.6 m, smart 10.6 m, smart 7.6 m, and smart probe 7.6 m) from 4 different distances (0.5, 1, 2, and 4 m) at head phantoms made of either 5- or 7-mm-thick polyurethane spheres covered with a thin layer of gelatine and buckskin. The piercing depths were recorded by computed tomographic scanning.All tested cartridges managed to pierce the head phantoms. Piercing depths of up to 6.6 mm in the 5-mm heads and depths of almost 5 mm in the 7-mm heads were recorded. Deepest piercing depths were attained with firing distances of 2 m or less.Our results showed that all tested CEW probes are capable of piercing the skull and that shorter firing distances tend to lead to deeper piercing depths.

Correlation of fat embolism severity and subcutaneous fatty tissue crushing and bone fractures.

Pulmonary fat embolism (PFE) is frequently encountered in blunt trauma. The clinical manifestation ranges from no impairment in light cases to death due to right-sided heart failure or hypoxaemia in severe cases. Occasionally, pulmonary fat embolism can give rise to a fat embolism syndrome (FES), which is marked by multiorgan failure, respiratory disorders, petechiae and often death. It is well known that fractures of long bones can lead to PFE. Several authors have argued that PFE can arise due to mere soft tissue injury in the absence of fractures, a claim other authors disagree upon. In this study, we retrospectively examined 50 victims of blunt trauma with regard to grade and extent of fractures and crushing of subcutaneous fatty tissue and presence and severity of PFE. Our results indicate that PFE can arise due to mere crushing of subcutaneous fat and that the fracture grade correlated well with PFE severity (p = 0.011). The correlation between PFE and the fracture severity (body regions affected by fractures and fracture grade) showed a lesser significant correlation (p = 0.170). The survival time (p = 0.567), the amount of body regions affected by fat crushing (p = 0.336) and the fat crush grade (p = 0.485) did not correlate with the PFE grade, nor did the amount of body regions affected by fractures. These results may have clinical implications for the assessment of a possible FES development, as, if the risk of a PFE is known, preventive steps can be taken.

Unusual foreign bodies visualized by postmortem computed tomography in a deceased with borderline personality disorder.

The objective of this case report is the visualization and assessment of ingested or inserted foreign bodies by postmortem computed tomography and autopsy. The presence of foreign objects in the gastrointestinal tract involves, among many other medical subdisciplines, the fields of forensic medicine and psychiatry. We present a case of an 18-year-old female Caucasian with borderline personality disorder who was found unconscious in a closed psychiatric ward with suspected ingested foreign bodies. Cardiopulmonary resuscitation was unsuccessful. Postmortem computed tomography revealed several sharp foreign bodies in the intestine varying in radiodensity and shape but not perforating any anatomic structures. The autopsy showed well-preserved tablets in the intestine, a few inserted glass fragments and one metal fragment. Ultimately, fatal intoxication involving a mixture of opioids, benzodiazepines, neuroleptics and antidepressants resulted. This case illustrates the potential contribution of postmortem computed tomography in diagnosing, localizing and defining ingested and inserted foreign bodies in deceased as well as living individuals. Thus, diagnostic imaging might increase safety not only for the affected individuals but also for medical staff.

The gas bubble sign-a reliable indicator of laryngeal fractures in hanging on post-mortem CT.

OBJECTIVE: The purpose was to evaluate the presence of gas in the tissue adjacent to the laryngeal structures, "the gas bubble sign", in cases of hanging as a diagnostic indicator of neck trauma. METHODS: In this study, post-mortem CT (PMCT) scans and autopsies of 35 victims of hanging were examined to reveal age-dependent changes, laryngeal fracture, fracture location and the presence of gas. A matched group with cardiac arrest or intoxication was used as controls (n = 35). An autopsy was performed in each case. RESULTS: Incomplete suspension was the most common method in hanging. The thyroid horns (90.5%) were identified as the most vulnerable location for fractures. Laryngeal deformity and dislocation, which was only detected on PMCT, was observed in 57.1% and was concomitant with fractures in 83.3%. Laryngeal fractures are more common with advanced age (>40 years, 88.9%) and less common in younger subjects (<40 years, 29.4%). The gas bubble sign with regard to laryngeal fractures yielded a sensitivity of 79.2%, a positive predictive value of 95%, a specificity of 90.9%, a negative predictive value of 34.5% and an accuracy of 83%. CONCLUSION: The complex evaluation of the larynx is profoundly supported by PMCT and the detection of the gas bubble sign as a diagnostic indicator of neck trauma. This relevant diagnostic finding might aid in not only post-mortem cases but also clinical cases, for patients who survive an assault to the neck. Advances in knowledge: (1) The gas bubble sign is a diagnostic indicator of neck trauma in not putrefied bodies. (2) PMCT supports evaluation of trauma to the neck in hanging tremendously. (3) The diagnostic finding of gas located at the laryngeal structures may not only aid in post-mortem cases but also clinical cases of people who survive an assault to the neck.