Medical criminalistics

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.

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.

Fat from contused adipose tissue may cause yellow discoloration of clothes in blunt trauma victims

In some fatalities from intense blunt trauma, the victims' clothes show strikingly yellow discoloration being in topographic correspondence with lacerated skin and crush damage to the underlying fatty tissue. This phenomenon is especially pronounced in light-colored textiles such as underwear made of cotton and in the absence of concomitant blood-staining. The constellation of findings seems to indicate that the fabric has been soaked with liquid body fat deriving from the contused adipose tissue. To check this hypothesis, textiles suspected to be contaminated with fat were investigated in 6 relevant cases. GC-MS-analysis proved the presence of 11 fatty acids. The fatty acid composition was similar to that of human adipose tissue with a high proportion of oleic acid (18:1). In total, the morphological and chemical findings demonstrated that the yellow discoloration of the victims' clothes was caused by fat from traumatized adipose tissue.

Modification of hematoma findings in the breast region

Subcutaneous bruises caused by blunt injury are common findings in medicolegal case work. If the hematoma involves the anterior thoracic wall, bruises are mostly absent in the region of the nipples and the surrounding areola. A similar phenomenon has already been described for hypostatic skin hemorrhages. A possible explanation for both phenomena is the special tissue texture in the nipple-areola complex. Based on four cases from the forensic autopsy material and two cases from clinical forensic examinations, the macromorphological findings and the histological correlates are presented.

Transorbital impalement injury with massive intracranial lesion not detected by cranial CT scan

An extraordinary case of transorbital penetration injury is presented. A 24-year-old male patient was involved in a fight and was pushed against a shelf. He immediately lost consciousness and was brought to hospital. A cranial computed tomogaphy (CT) scan showed a hemorrhage and brain edema over the left hemisphere with orbital roof fracture. A decompressive craniectomy was performed. Intraoperatively, an orbital roof fracture with penetration of the frontobasal dura could be seen which could not be explained by the trauma mechanism. The postoperative magnetic resonance imaging (MRI) with susceptibility-weighted image (SWI) showed two injury tracks from the orbit through the brain which appeared to be penetration injuries. The forensics department was consulted and penetration by a falling candleholder was found to be the cause of the injuries. In this case, the cranial CT alone did not show any indication of a penetration injury. Only MRI revealed the penetration track, which stresses the diagnostic value of this modality and especially the SWI in cases where the trauma mechanism does not correspond to the injury shown in the CT scan.

Philemon and Baucis Death?

When two human corpses are found in temporal and locational context the assumption of a non-natural cause of death is close at hand. Suicide, extended suicide, homicide or accident (particularly with carbon monoxide) come to mind. When, however, a natural cause of death emerges for both after autopsy and further examinations, this provokes the question whether this incidence is coincidental. In our two presented cases, a married couple each was found dead together. In both cases, the wife needed nursing and was being cared for by a husband who died of cardiac disease shortly before the wife died. In one case, the wife died of acute uncompensated chronic congestive heart failure. In the other case, the cause of death of the wife was hypovolemic shock due to acute gastrointestinal bleeding from recurrent gastric mucosal erosion. It is to be discussed for both cases whether, given the pre-existing illness, the acute stress of the situation in view to the husbands' death may at least have favored the occurrence of death and may, thus, have led to the criminologically conspicuous situation of finding.

Ingestion of pointed objects in a complex suicide

A 51-year-old woman with a psychiatric history of depression and drug abuse was found hanged in her bedroom. The ligature was a scarf attached to the door handle. The autopsy findings suggested that two methods of suicide had been used one after the other. In the first stage, numerous nails, pins and needles were swallowed; in the second stage, the suicide was completed by hanging.