On a knife edge: A preliminary investigation of clothing damage using rounded-tip knives

Bladed weapons are frequently encountered in violent crime offences including street based and armed robberies, murder, sexual assaults and terrorism. A study was conducted involving four frequently encountered clothing fabrics: t-shirt (knitted cotton), denim jeans (twill woven cotton), long sleeved top (knitted synthetic blend), and skirt (non-woven faux leather) and five knives to investigate any damage resulting from a downward stabbing motion, with 300 stabs in total. Any resultant penetrating severance damage was then photographed, measured and analysed. Statistical analysis revealed significant differences between the stab hole size and shape, as a consequence of the design of a bladed weapon (in particular, the tip shape) that caused it. There is a notable correlation between the Assure knife (rounded tip) and no resulting severance damage, as the fabric surfaces were not breached with this knife. This suggests a clear alternative to pointed tip knife blades. These findings will be of interest to investigators of knife crime offences, crime-reduction units, knife manufacturers and practitioners, who share the goal of identifying a safer alternative to conventional knife blade design.     

Piquerism in homicide: A knife wound analysis of a sexually motivated serial killer

As part of a wider research project into paraphilic disorders and homicide, a case is presented of a piquerist who achieved sexual satisfaction through the infliction of stabbing wounds. Against a background of sexual domination with willing and unwilling sexual partners, the offender stabbed four men to death. A study of the resulting autopsy reports, in association with the offender's testimony and crime scene documentation, was undertaken to discern a piquerist crime scene signature. An excessive number of stabbing wounds, the targeting of sexual areas, and a variation in wound size and depth were found to be evidence of piquerism. Although there was opportunity to commit a sexual assault upon victims, the preference was to penetrate them with a knife. It is contended that, even without any evidence of sexual assault at a crime scene, a knife wound analysis can reveal a sexual motivation in some cases of homicide.     

A rare suicidal case of a ten-year-old child stabbing himself in the throat

A rare case is reported of a ten-year-old boy who committed suicide by stabbing himself in the throat with a pointed knife. Possibility of an accidental injury was excluded by the autopsy findings; suspicion of a homicide by his father was cleared through the deposition of his sister. The reason of suicide was attributed directly to his father's severe scolding and indirectly to his mother's death two years before.     

Immunocytochemical examination of biological traces on knife blades

In cases of penetrating stab wounds by different knives it is highly relevant to prove which knife caused which injury, especially if one of the injuries was lethal. This is possible by immunocytochemical examination of cellular material remaining on the injuring blade because some organs have organ-specific antigen determinants such as alpha-l-fetoprotein in the liver cells or cardiac troponin I in the heart muscle cells, to which antibodies can bind. Even when penetrations occur through several layers of clothing, enough cells from the injured organ remain on the blade of a knife to allow immunohistochemical examination. These cells can be collected by means of adhesive film or wiping the blade and can be stained immunocytochemically. The organ specificity of the examined proteins allows proof of their origin. The present study shows that immunocytochemical alpha-l-fetoprotein and cardiac troponin I staining of the cells remaining on a knife blade enables proof of whether the knife blade injured the heart or the liver, or both.     

Pattern of findings in injuries caused by "survival knives"

Survival knives are designed as multi-purpose tools. Most models have a broad single-edged fixed blade, like a trail-knife or Bowie-knife. The back of the blade normally has saw teeth set either in single line or double crossed line. This adds a third function, sawing, to the two standard functions of the knife (stabbing and cutting). The saw edge leaves characteristic scrape marks on the skin; bony structures are grooved or completely severed. A case of homicide is taken to demonstrate that the pattern of injuries may indicate the use of a survival knife.     

Piercing the surface: A mechanical analysis of stabbing with household tools

Estimating the applied power during a stabbing incident, or estimating the minimal force necessary to penetrate the body with a certain weapon is a challenging task in forensic practice. A thorough forensic evaluation of stabbing forces needs objective numerical experimental data. Stabbing tests of 12 different weapons – including knives, a pair of scissors, a fork, screwdrivers, a rasp, a corkscrew, and a utility knife blade – were performed with a Mecmesin MultiTest-dV material tester on pork loin and ballistic gel to estimate the stabbing forces and dynamics. Penetration force (F_p) and maximal force (F_max) were recorded, and the registered force curves were analyzed. F_max was 159.8–212.07 Newton (N), 30.56–30.58 N, 168.9–185.48 N for various knives; 171.39–190.43 N for the pair of scissors, 233.6 N for the fork; 532.65–562.65 N, 370.31–367.19 N and 314.51–432.89 N for various screwdrivers, 44.14–56.62 N for utility knife during pork loin stabbing. The butter knife, corkscrew and rasp were not able to penetrate the pork loin, and the curved fork bent during stabbing. The results prove that weapon characteristics greatly influence the force necessary for penetration. Maximal stabbing force depends mostly on tip sharpness, and the force sharply decreases after penetration occurs, which indicates that edge sharpness is not as important as tip characteristics during stabbing perpendicular to skin surface. The penetration force during stabbing with a pair of scissors is comparable to the penetration force of knives. Stabbing with screwdrivers generally needs larger force than average knives but depends greatly on screwdriver size.     

Can a machine be used to replicate the biomechanics of human stabbing performance?

A human performance trial was conducted where the stabbing actions of 40 participants were investigated. A range of factors were assessed such as the action used when the blade shape and familiarity of the knife changed. A qualitative evaluation of these factors was presented in an earlier paper to precede the analysis of quantitative kinematic data in this paper. The data from participants was then compared to that obtained from a stabbing machine.A motion analysis system was used to measure parameters such as the joint angular displacement and absolute linear velocity at impact. Motion data was collected using a 12-camera Vicon MX motion analysis system. Results indicated that the mean absolute linear velocity of overarm stabbing actions was consistently higher than the underarm actions.Forensic textile damage examinations often involve testing of edged weapons by manually performing stabbing actions. An underlying fundamental limitation of manual simulation experiments is the natural variation inherent in human performance. Sufficient control measures can be implemented to successfully use manual simulation experiments in forensic testing and therefore this is the accepted practice. However, performance can be improved using a stabbing machine. A custom-built instrumental stabbing device has been shown to operate within the same parameters of the human participants and is therefore suitable for use in casework.     

An assessment of human performance in stabbing.

Stab-resistant body armour is now becoming a standard item of equipment for police officers in the United Kingdom. In the UK these are usually required to have a stab resistance as specified by the Police Scientific Development Branch KR42 standard [G. Parker, PSDB Stab Resistant Body Armour Test Procedure, Police Scientific Development Branch, Publication No 10/93, 1993]. There are several other test standards, all of which specify that body armour must resist penetration by a specific blade type delivered at a specific energy level or range of levels. However, the actual range of energy levels specified varies over almost an order of magnitude and the basis for these levels is not clearly defined. This paper describes tests to determine the energy range and characteristics of stabbing actions that might be directed against stab resistant body armour by an assailant. The energy and velocity that can be achieved in stabbing actions has been determined for a number of sample populations. Volunteers were asked to stab a target using an instrumented knife that measured the axial force and acceleration during the stabbing. The maximum energy obtained in underarm stabbing actions was 64 J whilst overarm stabbing actions could produce 115 J. The loads produced on contact with the target often approached 1000 N.     

Chronology of a homicide and an attempted suicide by DNA analysis of selected blood stains on the weapon (knife)]

A five-year-old boy was fatally injured by a stab and a cut to the throat. The suspected offender, an acquaintance of the victim's mother, stated that he had been disturbed by the boy while attempting suicide and had therefore killed the boy. The suspect showed superficial cuts on both wrists and three shallow stabs on the right-hand side of the abdomen. The purpose of the forensic investigations was to answer the question if the suspect's statement could be confirmed or if the attempted suicide took place after killing the boy. The blood-smeared blade of the knife was divided into different sectors with the cutting edge and the tip of the blade being examined separately from the sides. The blood traces from the different blade sectors were then typed in 12 different DNA regions by PCR (polymerase-chain-reaction). It could be demonstrated that the strong blood traces on the sides of the blade originated from the victim alone, whereas in the area of the edge and the tip of the blade the amount of the victim's blood was negligible compared with that of the suspected offender. The explanation for this finding is that in the areas of the edge and the tip of the knife the blood of the victim must have been replaced by the blood of the suspected perpetrator, which means that the suicidal injuries were the last to be caused by the knife.     

Puncture wounds caused by glass mistaken for with stab wounds with a knife

Three cases are presented where fatal puncture wounds caused by broken glass were very similar to stab wounds inflicted by a knife with a single-edged blade. Thus, all three cases caused a murder investigation to be initiated. It could only be determined that these wounds had been caused by glass after a detailed forensic autopsy. In two of the three cases, the only evidence for this was the identification of glass fragments in the wounds. The importance of X-ray examinations is underlined because modern glass in common use is radiopaque. Glass fragments lodged in the wounds can reduce the loss of blood and thus, prolong the capacity to act despite severe injuries.     

Defined contusion marks caused by the knife handle]

If in inflicting a stab wound the knife is vigorously pushed in up to the end of the blade, this does not only cause cutting of the tissue, but also a blunt traumatization. The resulting abrasions can correspond with the respective construction parts (handle, handguard, devices for fixing the open blade) as to position, shape and size, thus allowing conclusions as to the shape of the instrument used. Incomplete, one-sided marks of the handle suggest an oblique-angled stab. The presence of a contusion mark shows that the blade penetrated completely, which makes it easier to draw conclusions as to the length of the blade from the depth of penetration. The reconstruction possibilities are demonstrated on the basis of three autopsies (homicide cases with different types of knives).     

Kinematics of four methods of stabbing: a preliminary study

Despite considerable research and development into stab-resistant clothing, no data exists which provides valid data for knife-body contact speeds which may be used to ensure that an appropriate and standard protection level is provided. Such data can only be obtained by a quantitative kinematic analysis of the stabbing movement. Two-dimensional video techniques (50 Hz) were used to record images of subjects (n = 10) performing each of four stabbing actions; Long Over (LO), Long Under (LU), Short Over (SO), Short Under (SU). Images were digitised from a minimum of ten frames pre-, to at least six frames post-blade entry. A two-way analysis of variance applied to selected kinematic parameters revealed significantly higher (P < 0.01) blade entry speeds for LO and LU as compared to SO and SU, respectively. This was due to the extra distance over which knife speed could be increased in the former conditions. Significantly greater shoulder joint angular velocities were found for LU and SU conditions, whilst for the elbow joint, conditions LO and SO were significantly greater (P = 0.000008). This suggests that the entry speeds during LO and SO are derived from a greater contribution from elbow extensor muscles, whilst those for LU and SU are derived from a greater contribution from the shoulder flexors. It was concluded that two separate kinematic strategies were employed by subjects, and that the maximum speed which may be generated during stabbing is influenced by the manner in which the knife is held.     

Suicide by skull stab wounds: a case of drug-induced psychosis

Suicide by stabbing to the head and/or driving sharp objects into the skull is of extreme rarity. This article reports the case of a 27-year-old man, who committed suicide by multiple knife stabs and cuts to the head, the torso, one shoulder and the forearms. Autopsy showed a perforating wound of the skull and the 10-cm long broken blade of the knife being still embedded in the right temporal lobe of the brain. The deceased had no history of psychiatric illness but was currently treated by mefloquine, a quinine derivative associated with a high rate of psychiatric adverse effects. Toxicological examination confirmed a recent intake of mefloquine together with chloroquine, another antimalarial drug. To our knowledge, this is the first report of a completed suicide with very strong evidence of mefloquine implication. Discussion focuses upon mefloquine-induced psychiatric disorders and highlights the importance of performing toxicological investigations in cases of unusual suicides.     

A comparison of fatal with non-fatal knife injuries in Edinburgh

Assault using a knife is a common problem in the United Kingdom. Between February 1992 and December 1996, 120 individuals died or received hospital treatment in Edinburgh after being assaulted with a knife. Twenty individuals (17%) died as a result of their injuries. Comparison of the survivors with non-survivors revealed both groups to have similar age and sex distributions, but those who died had significantly more severe injuries when scored according to the Abbreviated Injury Scale. Eight individuals died of unsurvivable chest injuries at the scene of the attack and of the remainder, only five reached hospital with signs of life. Analysis of hospital treatment using TRISS methodology revealed there to be two unexpected survivors and no unexpected deaths. The risk of death appears to depend mostly upon injuries sustained and also to a lesser extent upon other factors such as alcohol consumption and the presence of a bystander capable and willing to request emergency medical assistance. There does not appear to be much potential to save lives by improving hospital treatment for those assaulted with a knife in Edinburgh. Instead, greater focus needs to be placed upon rapid transfer to hospital and upon restricting the possession and use of knives.     

Skull Fracture with Brain Expulsion in a One-Level Jumping-Fall

Abstract:  Here presented is the case of a one-level jumping-fall with extensive skull fractures and brain expulsion. The body was found on the basement floor at the foot of the stairs. At the autopsy, the skull was extensively fractured, with about half of the brain expulsed several feet away from the body. The cause of death was established as a craniocerebral trauma with brain expulsion. The circumstances and manner of death were still unclear at that time. A low fall seemed very unlikely considering the severity of the skull and brain damage. The police investigation clearly revealed that the man, in a paranoid psychotic state, attacked his wife with a knife and then was witnessed by his children to have hit his head several times with a hammer. Afterwards, they saw him running to the top of the basement stairs and jumping to the bottom of the stairs head first.     

Inadvertent clavicular fractures caused by "chiropractic" manipulations in an infant: an unusual form of pseudoabuse

A nine-month-old child was found unresponsive in his crib, five hours after his last feeding. At autopsy, there were no external or internal signs of abuse or neglect, and a few visceral pleural and epicardial petechiae were consistent with the sudden infant death syndrome (SIDS). However, postmortem total body radiographs revealed healing, symmetrical clavicular fractures and a healing left medial humeral epicondyle fracture. The parents had no explanation for these injuries and denied causing any harm to the child. The location and nature of the fractures strongly suggested abusive origin, and the case was reported to the police and the district attorney's office as child abuse. During the investigation, information from the parents indicated that the child had undergone "chiropractic" manipulations by an unlicensed therapist, between three and four weeks prior to death, to correct supposed "shoulder dislocations." This time interval correlated with the histologic age of the injuries, and the history explained their unusual bilateral location and appearance. The parents were exonerated of abuse charges, and the death was ascribed to SIDS.     

Injury pattern on the hand after slipping onto the blade during a knife attack--a contribution to the differential diagnostic classification of sharp force injuries of the upper extremities

Differential diagnosis of injuries caused by accidental slipping of the hand onto the blade of a knife includes self-inflicted injuries (e.g. to simulate an offense) as well as active and passive defense injuries indicative of the involvement of another party. The injury pattern on the hands of five perpetrators who suffered accidental cuts during knife attacks, as seen by the authors during the clinical forensic examination, is presented. The injuries were localized on the ulnar aspect of the thumb facing the index finger, the radial aspect of the index finger facing the thumb and variable sites on the flexor or extensor side of the middle and ring fingers. Especially in those cases in which the injuries of the victim (e.g. involvement of bony structures) and the dominant hand of the perpetrator are known, additional information for the reconstruction of the course of events may be derived from the cut wounds occurring during the knife attack as the hand slipped onto the blade.     

Determination of questionable suicide as a homicide by studies of criminal stains

In a woman found dead with cuts on both arms in a domestic sauna plastered with blood were assumed next to a bleed to death. The question self-infliction or by a third party of arm injuries could not be decided. By investigation of blood traces only could be clarified the cause of death. The husband had strangled his wife and inflicted several cuts on both arms with a razor blade to simulate suicide. Afterwards, he also inflicted several cuts on himself with a razor blade with the intention of suicide. He survived these injuries.     

Alteration of the Death Scene After Self‐stabbing: A Case of Sharp Force Suicide Disguised by the Victim as a Homicide?

This paper reports a case of a 72‐year‐old woman who was found dead in her bedroom with a 4 cm vertical stab wound in the abdomen. A bloodstained knife was found in the top drawer of her bedside table. The clothes worn by the victim showed no damage. A bloodstained vest and a sweater with frontal incisions were found far from the victim, in the bathroom and in the bedroom respectively. Several bloodstains were found in every room of the apartment. The evidence found during the forensic examination and, in particular, the Bloodstain Pattern Analysis, led the investigators to determine the manner of death, being consistent with a suicide with a long‐lasting physical activity after self‐stabbing. This report describes an unusual case of “disguised suicide,” in which the victim tried to cover‐up the suicide by changing her clothes and concealing the weapon, in the last minutes of her life.