How taphonomic alteration affects the detection and imaging of striations in stab wounds.

Stabbing with a kitchen knife is a common method of homicide in Europe. Serrated knives may leave tool markings (striations) in tissues. Documentation of striations is necessary for their use as forensic evidence. Traditional methods (physical casting and photography) have significant limitations, and micro-computed tomography (micro-CT) has been trialled in cartilage to "virtually cast" wounds. Previous research has shown the proportion of striations in cartilage falls following decomposition. This project has investigated the effects of taphonomic alteration and documentation methods of striations in porcine skin. Fresh, decomposed, mummified, burnt and waterlogged stab wounds in a porcine analogue were excised and imaged using photography, stereo-optical microscopy and micro-CT. The proportion of striations in each taphonomic group was determined from the images by independent analysts. Striations were observed more frequently in serrated blade wounds, although they were also identified in non-serrated blade wounds. The proportion of wounds showing striations declined following decomposition. An inversely proportional linear correlation between advancing decomposition and proportion of striations existed. Dehydration (mummification and burning) rendered serrated and non-serrated blade wounds indistinguishable. Water composition affected the preservation of striations. Identification of striations gradually declined after decomposition in tap water, but persisted to a point when left in brackish water. All three techniques imaged striations; however, the optimum technique was stereo-optical microscopy due to practical advantages and specific limitations affecting photography and micro-CT. This study demonstrates the effects of taphonomic alteration on striations and suggests stereo-optical microscopy is the optimum method for their documentation.

Forces generated in stabbing attacks: an evaluation of the utility of the mild, moderate and severe scale.

The commonest way of killing in the UK is by a sharp instrument. Knight reported in 1975 that it is impossible to discern with any degree of certainty the degree of force used to create a stab wound. Despite this, expert witnesses continue to approximate the degree of force used for their reports and evidence in court. It is usually subjectively categorized as mild, moderate or severe, based solely on the examination of the wound. We undertook a study considering forces generated in a range of blunt trauma actions, using a novel force plate dynamometer to measure the peak forces obtained by adult male and female volunteers. We then studied forces generated by stabbing skin simulants and porcine samples with knives and screwdrivers. Men generated more force than women during stabbings which was found to be equivalent to somewhere between the blunt trauma actions of pushing a button to a single-handed push. When asked to stab using what they thought was mild, moderate and severe force, although volunteers were able to actively decide the force used, the actual force was found to be influenced by the weapon, sex of the individual, hand used and biological/anatomical site penetrated. This study shows that the forces generated by volunteers in mild, moderate and severe stabbing tests in almost all cases were significantly greater than the forces required for skin penetration. We suggest that the use of subjective force scales is inappropriate. Rather than use of a subjective scale, we suggest that the force required in any stabbing requires investigation in four areas: the tip radius of the weapon, minimal force required for penetration, the sex of the assailant and whether the force required for penetration is greater than that that can be generated by a person stabbing. This allows for the use of an evidence-based two-tier scale to suggest the force required.

Perimortem trauma in King Richard III: a skeletal analysis.

BACKGROUND: Richard III was the last king of England to die in battle, but how he died is unknown. On Sept 4, 2012, a skeleton was excavated in Leicester that was identified as Richard. We investigated the trauma to the skeleton with modern forensic techniques, such as conventional CT and micro-CT scanning, to characterise the injuries and establish the probable cause of death. METHODS: We assessed age and sex through direct analysis of the skeleton and from CT images. All bones were examined under direct light and multi-spectral illumination. We then scanned the skeleton with whole-body post-mortem CT. We subsequently examined bones with identified injuries with micro-CT. We deemed that trauma was perimortem when we recorded no evidence of healing and when breakage characteristics were typical of fresh bone. We used previous data to identify the weapons responsible for the recorded injuries. FINDINGS: The skeleton was that of an adult man with a gracile build and severe scoliosis of the thoracic spine. Standard anthropological age estimation techniques based on dry bone analysis gave an age range between 20s and 30s. Standard post-mortem CT methods were used to assess rib end morphology, auricular surfaces, pubic symphyseal face, and cranial sutures, to produce a multifactorial narrower age range estimation of 30-34 years. We identified nine perimortem injuries to the skull and two to the postcranial skeleton. We identified no healed injuries. The injuries were consistent with those created by weapons from the later medieval period. We could not identify the specific order of the injuries, because they were all distinct, with no overlapping wounds. Three of the injuries-two to the inferior cranium and one to the pelvis-could have been fatal. INTERPRETATION: The wounds to the skull suggest that Richard was not wearing a helmet, although the absence of defensive wounds on his arms and hands suggests he was still otherwise armoured. Therefore, the potentially fatal pelvis injury was probably received post mortem, meaning that the most likely injuries to have caused his death are the two to the inferior cranium. FUNDING: The University of Leicester.

Forces required for a knife to penetrate a variety of clothing types.

In stabbing incidents, it is usual for the victim to be clothed and therefore a knife penetrates both clothes and skin. Clothes (other than leather) have been thought to make little difference to the penetration force. However, there is little quantitative data in the literature. In this study, a range of clothes have been tested, either singly or in layers of, for example, T-shirt and shirt, to quantify the additional force required when clothes are present. A materials testing system has been used to test the penetration force required to stab through clothes into a foam-silicone rubber skin simulant. The results show that the force required can be significantly different, particularly when layers of clothing are penetrated. A cotton t-shirt adds c. 8 N to the penetration force, while a T-shirt and jacket can add an additional 21 N. The results allow a more quantitative assessment of forces required in stabbing.

Enhanced detection of thromboemboli with the use of targeted microbubbles.

BACKGROUND AND PURPOSE: Targeted ultrasound contrast agents have recently been developed to adhere selectively to specific pathogenic materials such as plaque or thrombus. Administration of such microbubbles has potential to aid transcranial Doppler ultrasound (TCD) detection of emboli and to act as markers for distinguishing one embolic material from another. The purpose of this study was to investigate whether TCD detection of circulating thrombus emboli would be enhanced by the addition of targeted microbubbles. METHODS: Binding of microbubbles to the surface of the thrombus was confirmed by scanning electron microscopy. Targeted and control bubbles were then introduced to thrombus and tissue-mimicking material circulated under pulsatile-flow conditions in an in vitro flow rig. Embolic signal intensities before and after introduction of the bubbles were measured by TCD. RESULTS: Targeted microbubbles enhanced TCD signal intensities from thrombus emboli by up to 13 dB. The bubbles were capable of binding to moving thrombus when injected into the flow circuit in low concentrations ( approximately 36 bubbles per 100 mL) and were retained on the thrombus under pulsatile-flow conditions. Signal intensities from similarly sized pieces of tissue-mimicking material were not enhanced by injection of targeted bubbles. CONCLUSIONS: Injection of appropriately targeted microbubbles significantly enhances TCD detection of circulating thrombus emboli in vitro.

Effect of titanium carbonitride (Ti(C,N)) decomposition on failure mechanisms in Inconel 617 alloy.

Titanium Carbonitride (Ti(C,N)) decomposition in Inconel 617 alloy creep-exposed at 650°C for 574 hours is reported using analytical electron microscopy techniques. Cr-enriched M23C6-type carbides enveloped in fine gamma prime particles thought to be precipitated from the decomposition reaction are observed in the alloy. The morphology of the M23C6 carbides is irregular and blocky and the particle size up to 5 µm, whereas the morphology of gamma prime particles is mostly spherical and up to 30 nm in size. Intergranular carbides are mostly secondary precipitates of the M23Cc type (M predominantly Cr) and these respond to solution heat treatment and precipitate on the grain boundaries as a result of ageing. The ability of intragranular MX to decompose is sensitive to the N content, high N resists decomposition. Decomposed intragranular MX provides an excess source of C which can react locally with Cr to form heat treatable intragranular fine Cr23C6 precipitates. M6C can segregate in interdendritic locations during melting which may be the reason for high content of Mo in M23C6. These precipitates are generally very small and contribute to an additional hardening effect and are the reason for the onset of voiding and cracking along the grain boundaries that ultimately lead to a reduced creep rupture life.

Lead theft--a study of the "uniqueness" of lead from church roofs.

In the United Kingdom, theft of lead is common, particularly from churches and other public buildings with lead roofs. To assess the potential to distinguish lead from different sources, 41 samples of lead from 24 church roofs in Northamptonshire, U.K, have been analyzed for relative abundance of trace elements and isotopes of lead using X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry, respectively. XRF revealed the overall presence of 12 trace elements with the four most abundant, calcium, phosphorus, silicon, and sulfur, showing a large weight percentage standard error of the mean of all samples suggesting variation in the weight percentage of these elements between different church roofs. Multiple samples from the same roofs, but different lead sheets, showed much lower weight percentage standard errors of the mean suggesting similar trace element concentrations. Lead isotope ratios were similar for all samples. Factors likely to affect the occurrence of these trace elements are discussed.