Thomas Colard

Experimental study of the expansion dynamic of 9 mm Parabellum hollow point projectiles in ballistic gelatin

We study in this paper the expanding behaviour of hollow point 9 mm Parabellum projectiles (Hornady XTP(®) and Speer Gold Dot(®)). We defined a deformation rate that takes into account both the diameter increase and the length reduction. We plotted the behaviour of this parameter versus impact velocity (we refer to this curve as the expanding law). This expanding law has been plotted for different gelatin weight ratios and different gelatin block lengths. We completed our experiments with a set of high speed movies in order to correlate the deceleration to the state of expansion and size of the temporary cavity. Our results pointed out that full expansion is reached shortly after the projectile fully penetrates the gelatin. This result shows that the key point to accurately simulate human body interaction with a hollow point projectile is to accurately simulate the interface (skin, skull, clothes thoracic walls). Simulating accurately organs is only an issue if a quantitative comparison between penetration depths is required, but not if we only focus on the state of expansion of the projectile. By varying the gelatin parameters, we discovered that the expanding law exhibits a velocity threshold below which no expansion occurs, followed by a rather linear curve. The parameters of that expanding law (velocity threshold and line slope) vary with the gelatin parameters, but our quantitative results demonstrate that these parameters are not extremely critical. Finally, our experiments demonstrate that the knowledge of the expansion law can be a useful tool to investigate a gunshot in a human body with a semi-jacketed projectile, giving an estimation of the impact velocity and thus the shooting distance.

Bilateral fractures of the scapula: Possible archeological examples of beatings from Europe, Africa and America

Traumatic injuries to the scapula have received little attention in the paleopathological literature. They are rarely encountered in medical emergencies today due to the overlying muscles that protect the bone; they comprise just 1% of all fractures. This collaborative project brings together five cases of bilateral fractures of the scapulae in four ancient populations from three different time periods and three continents (France, Sudan and USA). It is thus an opportunity to interpret bilateral scapula fracture etiology by suggesting a cause that could have been present in all contexts, namely direct trauma such as might take place during beating with heavy sticks or other blunt force weapons. We also argue that oval defects with rounded margins in scapular bodies are less likely to be congenital anatomical variants than the result of healed trauma.

3D-MSCT imaging of bullet trajectory in 3D crime scene reconstruction: Two case reports

Postmortem investigations are increasingly assisted by three-dimensional multi-slice computed tomography (3D-MSCT) and have become more available to forensic pathologists over the past 20years. In cases of ballistic wounds, 3D-MSCT can provide an accurate description of the bullet location, bone fractures and, more interestingly, a clear visual of the intracorporeal trajectory (bullet track). These forensic medical examinations can be combined with tridimensional bullet trajectory reconstructions created by forensic ballistic experts. These case reports present the implementation of tridimensional methods and the results of 3D crime scene reconstruction in two cases. The authors highlight the value of collaborations between police forensic experts and forensic medicine institutes through the incorporation of 3D-MSCT data in a crime scene reconstruction, which is of great interest in forensic science as a clear visual communication tool between experts and the court.

Skull wounds linked with blunt trauma (hammer example). A report of two depressed skull fractures – Elements of biomechanical explanation

The lesions of the skull following perforating traumas can create complex fractures. The blunt traumas can, according to the swiftness and the shape of the object used, create a depressed fracture. The authors describe through two clinical cases the lesional characteristic of the blunt traumas, perforating the skull using a hammer. In both cases the cranial lesions were very typical: they were geometrical, square shaped, of the same size than the tool (head and tip of the hammer). On the outer table of the skull, the edges of the wounds were sharp and regular. On the inner table, the edges of the wounds were beveled and irregular. The bony penetration in the depressed fracture results from a rupture of the outer table of the bone under tension, in periphery, by the bend of the bone to the impact (outbending) and then, from the inner table with comminuted bony fragmentation. Breeding on the fractures of the size and the shape of the blunt objects used is inconstant and differs, that it is the objects of flat surface or wide in opposition to those of small surface area. Fractures morphologies depend on one hand on these extrinsic factors and on the other hand, of intrinsic factors (structure of the bone). To identify them, we had previously conducted experimental work on cranial bone samples. The bone was submitted to a device for three-point bending. This work had shown properties of thickness and stiffness of the various areas of the vault. Our cases are consistent with these results and illustrate the variability of bone lesions according to region and mode of use of blunt weapons. Many studies have identified criteria for identification of the weapons and the assistance of digital and biomechanical models will be an invaluable contribution with this aim in the future.

Specific Patterns of Canine Scavenging in Indoor Settings

Postmortem animal mutilations due to domestic dogs in isolated domestic deaths are taphonomic modifications regularly observed by forensic pathologists. They are rarely described in the literature; however, even though they present specific patterns. Through 41 cases, 10 at the forensic institute in Lille (France) and 31 at the New York City Office of Chief Medical Examiner (USA), plus 22 cases from the literature, specific locations and patterns of postmortem scavenging lesions are proposed. These lesions are mainly distributed in three locations: the face, especially the nose and the mouth (73.1%), the neck (43.1%), and the arm (shoulder/upper limb [29.2%], hand [26.8%]). We discuss the time span between death and scavenging, the consequences on identification, and comparison with outdoor settings. Outdoor scavenging lesions are mainly located on the trunk and limbs usually sparing the head, which strongly differs from indoor distribution and imply different animal motivations.

New Insights on the Composition and the Structure of the Acellular Extrinsic Fiber Cementum by Raman Analysis

Acellular extrinsic fiber cementum is a mineralized tissue that covers the cervical half of the tooth root surface. It contains mainly extrinsic or Sharpey’s fibers that run perpendicular to the root surface to anchor the tooth via the periodontal ligament. Acellular cementum is continuously and slowly produced throughout life and exhibits an alternating bright and dark pattern under light microscopy. However, although a better understanding of the structural background of acellular cementum is relevant to many fields, such as cementochronology, periodontology and tissue engineering, acellular cementum remains rarely studied and poorly understood. In this work, we studied the acellular cementum at the incremental line scale of five human mandibular canines using polarized Raman spectroscopy. We provided Raman imaging analysis and polarized acquisitions as a function of the angular orientation of the sample. The results showed that mineral crystals were always parallel to collagen fibrils, and at a larger scale, we proposed an organizational model in which we found radial collagen fibers, “orthogonal” to the cementum surface, and “non-orthogonal” fibers, which consist of branching and bending radial fibers. Concerning the alternating pattern, we observed that the dark lines corresponded to smaller, more mineralized and probably more organized bands, which is consistent with the zoological assumption that incremental lines are produced during a winter rest period of acellular cementum growth.

Typical external skull beveling wound unlinked with a gunshot.

Lesions of the cranial vault resulting from firearms are traditionally described in forensic medical literature with many reports illustrating atypical bone lesions carried out to the skull by gunshot wounds. The authors present this report which illustrates an external beveled skull wound, associated with internal beveling damage, caused by a stabbing injury. A partially buried human skeleton was found in a forest. The examining of the skull revealed a hole resembling the exit wound caused by a bullet and two other smaller stab wounds. No typical entering bullet wound and no other bone lesions were found. During the course of the investigation, one of the perpetrators admitted to hitting the victim, using a sickle, and to hiding the body. For this purpose, he dragged the corpse with the sickle still implanted in the skull, using it as a hook. Upon retrieving the sickle, a piece of cranial vault was removed, thus creating an external beveled wound. In order to identify the mechanism which brought about this kind of lesion, experimental work was carried out on a human skull. In this particular case, the tip of the sickle penetrated into the bone, creating a lesion that would typically be produced with a stabbing instrument when applied with vertical force. When the body was dragged, using the sickle as a hook, this was a hand-produced vertical force, which was applied in the opposite direction. It caused the tearing of a piece of bone and the creation of an outer bevel. This atypical lesion should be made known to medical examiners and pathologists in order to help investigating and understanding of the circumstances of injuries.

Use of larder beetles (Coleoptera: Dermestidae) to deflesh human jaws

We describe new experimental data for the defleshing of human bones using larder beetles (Dermestes haemorrhoidalis) (Küster, 1852). Although the ability of larder beetles to feed on vertebrate remains has been, and still is, used by taxidermists to deflesh skulls and bones, this method has never been documented from a quantitative perspective and has over time become ignored in most forensic anthropology or odontology laboratories. To promote the rational and efficient use of this method, we performed experiments to estimate the quantity of food consumed by larvae. From the 2nd instar to nymphosis, each larva consumed a mean of 0.13±0.03 g of dry beef muscle. We then used 100±50 D. haemorrhoidalis adults and 100±50 larvae to deflesh human maxillae and mandibles sampled within a forensic context (victim identification). Each sample was weighed and photographed before, during and after the experiment. According to our experiments, 20-25 days were sufficient to completely deflesh all of the samples. We concluded that a small number of larder beetles can be used to efficiently deflesh human jaws. According to this result, the use of larder beetles appears to be an inexpensive, simple and efficient way to clean mandibles and maxillae. Furthermore, this method is DNA-safe (compared to usual maceration techniques) and thus allows the samples to be used for subsequent DNA and drug analyses.

Tuberculosis and survival in past populations: A paleo-epidemiological appraisal

Historical assessments of the last two centuries consistently placed tuberculosis as the leading cause of mortality. However, for earlier periods, we can only calculate the frequencies of archaeological bone lesions, which tell us little about the real impact of the disease on mortality. These lesions are usually observed in individuals who have developed immune resistance, which is visible as healed osteo-articular lesions. This study aimed to test the differential impacts of tuberculosis, cribra orbitalia and cribra femoris on adult survival and sex-based survival. We analyzed 28 French adult samples from the Antiquity and the Early Middle Ages. The age-at-death of 1480 individuals was estimated using cementochronology. Survival curves and median age-at-death were calculated to test new hypotheses that challenge the parasitic and deficiency theories of bone stress markers. Comparisons between carriers and non-carriers provided new information concerning the plausible causes of bone stress markers related to infections and TB. The most likely hypothesis is skeletal demineralization and osteoclastic resorption, which are usually observed close to tubercular granuloma or distant from active lesions. The bone marrow niche of Mycobacterium tuberculosis within CD271(+) BM-MSCs stem cells is the proposed explanation for the localized cortical resorption that is observed in bone stress markers.

The precision of micro-tomography in bone taphonomic experiments and the importance of registration

Micro-computed tomography (μCT) provides micrometric 3D images and has been used in forensic studies for anthropology pubis measurement or insect description for post mortem interval estimation. Studies have suggested using registration, a superimposing images method between a reference and a target. This technique avoids positioning bias and increase the precision of μCT. However, no clear study has reported the precision with μCT analysis before or after registration in a forensic field. One fresh post mortem sample of a human cranial vault was collected. Two successive μCT acquisitions (resolution 10μm) of it were performed without repositioning. The data from the second acquisition were copied and registered by two trained operators (operators 1 and 2). Operator 1 performed a second registration process after 1 week (operator 1 bis). The images were analysed. The bone volume (BV), bone surface (BS), number of trabeculae (TbN), trabecular thickness (TbTh) and mean trabecular distance (TbSp) were compared before and after registration. The mean (±SD), the coefficient of variation (%CV), and the precision error of the standard deviation absolute value and of the coefficient of variation between operators 1 and 2 (inter-subject variability) and between operator 1 and 1 bis (intra-subject variability) were calculated. We also collected the second phalanx of the 2nd, 3rd and 4th fingers on the hands of a second individual. Two successive scans (resolution 27μm) were performed without repositioning. A comparison (mean±SD of BV, BS, TbN, TbTh, TbSp) was made between the first and second scans with and without registration, and an ANOVA repeated measures procedure was performed. For the vault, we show that after 30 registrations for each operator (1, 2 and 1 bis), the mean and %CV were very close for each variable and between operators. For BV and BS, the difference in the mean value was approximately 0.01 (mm3 and mm2, respectively). The precision error was higher in the inter-subject registrations for each variable. The precision error magnitude for all variables was very low (<0.01) in absolute value and of %CV. For the fingers, the difference between the first and second scans may be approximately 50% without registration. We found that the second scan without registration is significantly different for BV (p=0.006), BS (p=0.007), TbN (p=0.019) and TbSp (p=0.002). Knowing the precision of the device (with and without registration) is important to ensure that the accuracy of the μCT results.