Microscopic analysis of sharp force trauma in bone and cartilage: a validation study

Death in the high mountains: Evidence of interpersonal violence during Late Chalcolithic and Early Bronze Age at Roc de les Orenetes (Eastern Pyrenees, Spain)

OBJECTIVES

To test a hypothesis on interpersonal violence events during the transition between Chalcolithic and Bronze Age in the Eastern Pyrenees, to contextualize it in Western Europe during that period, and to assess if these marks can be differentiated from secondary funerary treatment.

MATERIALS AND METHODS

Metric and non-metric methods were used to estimate the age-at-death and sex of the skeletal remains. Perimortem injuries were observed and analyzed with stereomicroscopy and confocal microscopy.

RESULTS

Among the minimum of 51 individuals documented, at least six people showed evidence of perimortem trauma. All age groups and both sexes are represented in the skeletal sample, but those with violent injuries are predominantly males. Twenty-six bones had 49 injuries, 48 of which involved sharp force trauma on postcranial elements, and one example of blunt force trauma on a cranium. The wounds were mostly located on the upper extremities and ribs, anterior and posterior. Several antemortem lesions were also documented in the assemblage.

DISCUSSION

The perimortem lesions, together with direct dating, suggest that more than one episode of interpersonal violence took place between the Late Chalcolithic and the Early Bronze Age in northeastern Spain. The features of the sharp force trauma indicate that different weapons were used, including sharp metal objects and lithic projectiles. The Roc de les Orenetes assemblage represents a scenario of recurrent lethal confrontation in a high mountain geographic context, representing the evidence of inferred interpersonal violence located at the highest altitude settings in the Pyrenees, at 1836 meters above sea level.

Recognition of the Presence of Bone Fractures Through Physicochemical Changes in Diagenetic Bone

Much research has focused on attempting to understand the drivers of bone diagenesis. However, this sensitive process is easily influenced by various factors, particularly the condition of the remains (i.e., whether they have been subjected to trauma). Previous research demonstrates that trauma can influence soft tissue decomposition, yet to date, no studies have looked at how bone fractures could affect bone diagenesis. To address this gap, two short timescale studies were conducted to investigate the influence of bone fractures on the physicochemical composition of disarticulated, partially fleshed animal remains. Disarticulated porcine bones were either fractured using blunt force or sharp force whilst fresh (producing perimortem damage), at 60 days producing postmortem damage (postmortem interval (PMI)), or left intact and left outside for up to 180 days post-fracture/240 days PMI. Retrieved bone sections were then analyzed for physicochemical differences using non-destructive methods, i.e., scanning electron microscopy energy dispersive spectroscopy and Fourier transform infrared spectroscopy with attenuated total reflectance. It was hypothesized that differences would be found in the physicochemical composition between the bones with fractures and those without after undergoing diagenetic change. The bone fractures significantly affected the elemental composition of bone over time, but structural composition initially remained stable. It was also possible to distinguish between perimortem and postmortem fractures using these two analytical techniques due to physicochemical differences. This research shows bone fractures can significantly alter the physicochemical composition of the bone during the postmortem period and have the potential to facilitate more accurate PMI estimations in forensic contexts.

Stereomicroscopic analysis of cut marks inflicted by a knife with blade damage

Skeletal cut mark analysis provides relevant information on the general class characteristics of suspect knife. However, there is a lack of research on the influence of blade damage on cut mark analysis. This study aimed to thoroughly investigate the effects of damaged knife blades on cut marks' morphological and morphometrical characteristics. Fifteen undamaged, non-serrated knives were used to cut human ribs to make control cut marks. The knife blades were then damaged by a series of cuts on the bones. A comparison was made between the control cuts and 3 groups of cut marks inflicted by blades that had been damaged to different degrees. The results showed that the damaged blades created wider cut marks than undamaged one. Kerf morphology was likely to imitate the cuts made by the serrated blades such as an elliptical shape, a V-shaped cross-section and the presence of coarse striations. Wear-related features can affect cut mark analysis as the marks left behind by blades damaged to different degrees showed dissimilar dimensions and morphologies. The findings of this study can be applied to a forensic investigation when cut marks were caused by a knife with a damaged blade.

Use of different imaging techniques in stab wound analysis

Stab wound analysis is a relatively new field of study in forensic science, and there is currently much debate regarding the effectiveness of the analysis due to a lack of validation studies. Furthermore, the underlying viewpoints on the success of stab wound analysis vary. Examination of cut marks, for example, can reveal a variety of characteristics which can be used to determine the type of weapon that was used to inflict them. However, published studies are not consistent when identifying knife blade characteristics, instead considering a wide variety of morphological aspects and their potential value in forensic scenarios. The existing research methodology is therefore inadequate to reliably inform in such contexts, and future experimental design should be influenced by the conditional variance in stabbings in order to provide reliable findings. The research presented here takes a systematic approach to the problem, compiling the published literature (up to September 2023) on the use of different imaging methods applied to stab wound examination to create a taxonomy to examine trends in methodological approaches in both research and investigative settings. This approach identified that published studies could be classified as either morphological or morphometrical, and further sub-classified based on their degree of success and the findings reached. This emphasises the importance of prioritising research into mark data, and the need for a multi-technique, multi-disciplinary approach. A decision tree was created to illustrate which mark attributes should be studied for which purpose, and using which imaging method(s). Furthermore, the research presented identifies two key areas in stab wound research which should be the focus of standardisation efforts, namely methodological procedures and mark characteristic collection. Knife markings are difficult to interpret, but further research and standardisation of kerf mark analysis, as highlighted here, will improve the efficiency and reliability of both forensic investigations and future experimental studies.

A proposed method for differentiating knives from cut marks on bone: A forensic anthropological approach

Knife cut marks have been extensively studied in forensic literature, and the results have been beneficial in identifying both the cut mark and implement type on bone. For this study, an assessment in differentiating knife cut marks has been attempted by using sword cut mark characteristics. In addition, a flowchart was created to assist in interpreting such marks. Knives of different serrations (non-serrated, macro- and micro-serrated) were used to inflict cut marks on pig ribs with a forward and backward stab thrust. The analysis revealed that some traits adapted from previous studies applied to knife cut marks and that non-serrated and serrated marks could be distinguished accurately using the flowchart. The distinction between different types of serrated blades was not as successful. However, results show that further research and development of the flowchart can be invaluable in similar analyses.

A probabilistic model for murder weapon identification using stab-marks in human ribs

The aim of this article is to provide a scientific and statistical basis to identify the murder weapon in stabbing cases from the geometric characteristics of the stab-marks left on human ribs. For this purpose, a quantitative predictive model is developed, based on geometric measurements of the stab-mark and its location along the rib. A general method based on Bayesian inference and probabilities is used for the model development, rather than a deterministic model given its inability in certain occasions to identify the murder weapon. Following the process explained in this article to collect the stab-mark information required, the complete probabilistic model exposed attained a high accuracy in the identification of the murder weapon between two macroscopically identical blades with a microscopic alteration in one of them (more than 90% of correct identification is achieved).

Dehydration-Induced alterations to sharp force trauma on Sus domesticus radii

Dehydration is a taphonomic process that affects nearly all skeletal remains, yet there is a dearth of evidence on this process within the forensic taphonomy literature. When considering the forensic implications of skeletal dehydration, a particular area of concern is sharp force trauma due to its global prominence in forensic cases. In an attempt to address these literature gaps and quantify the effects that dehydration has on skeletal elements, a controlled experiment subjected Sus domesticus (i.e., domestic pig) radii samples (n = 36) to laboratory-induced dehydration after they were inflicted with knife trauma. All samples were photographed pre- and post-dehydration; bone section and kerf mark length, width, and area were then measured from these photographs using ImageJ. Statistical analysis of pre- and post-dehydration samples showed that all measurements experienced significant (p ≤ 0.001) shrinkage, with bone sample area shrinking an average of 8.8 % and kerf mark area an average of 29.7 %. Alterations in length, width and area between the kerf marks and bone samples showed a weak, moderate, and strong correlation, respectively. These findings suggest that anthropological analysis may be affected by dehydration-induced shrinkage, highlighting the necessity of continued research into the effects of dehydration on skeletal trauma.

Cartilage Tissue in Forensic Science—State of the Art and Future Research Directions

Cartilage tissue performs many functions in the human body. The diseases and injuries affecting it are prevalent due to its slow regeneration rate. However, cartilage tissue is exceptionally important for its auspicious use in forensic medicine due to its slow postmortem degradation rate. The presented review summarizes the latest research on cartilage tissues and their current and potential applications in forensic science. It also describes the most important studies on using cartilage and its microscopic and macroscopic analyses to estimate the deceased age and determine postmortem interval (PMI) values and the crime weapon. Additionally, the review describes attempts to isolate DNA from cartilage tissue for individual identification. The review also mentions recent, less abundant studies on the cartilage in forensic toxicology and genetics. It points out further directions and prospects for research development on cartilage tissue and its promising use in forensic medicine

Bone Fracture Patterns and Distributions according to Trauma Energy

Background. This study investigates the effect of injury mechanism and energy on fracture patterns and distributions. Also, it compares differences in bone fracture patterns based on injury mechanism, gender, and age. Methods. Three thousand and sixty-six admitted patients with bone fractures were reviewed retrospectively, and the fractures were analyzed regarding age, gender, and mechanism of injury. Fractures were located in eleven bones. However, the forearm, hand, leg, and foot were considered one bone, and the fracture was then subclassified according to the anatomic position within each bone. Trauma energy was classified according to the mechanism of injury where simple falls were considered low-energy injury while falling from a height, road traffic accidents, bullet, and industrial injuries were considered high energy. Results. Males represented most of the patients, and most injuries occurred in adults. However, the male patients were more prone to injuries than females across all age groups below fifty years, women above fifty years were more frequent, and a third of females’ injuries occurred in the elderly. Simple falls represent two-thirds of the trauma mechanism, and falling from a height and road traffic accidents are the most common high-energy injuries and more prevalent in males. Scapular, clavicular, distal humerus, and shaft of long bones fractures were more prevalent in males. In contrast, females had a higher frequency of proximal humerus, proximal and distal femur, distal leg, and thoracic spine fractures. Industrial injuries are more frequent in males; thus, hand injuries are more frequent. Pathological fractures were higher in females, and spine and pelvic fractures were more associated with high-energy injuries. Conclusions. The trauma’s energy determines the bone injury’s extent and nature. Knowing the trauma mechanism is essential to expect the extent of injuries and construct preventive measures accordingly.

Application of 3D printing in assessment and demonstration of stab injuries

In stabbing related fatalities, the forensic pathologist has to assess the direction of wound track (thus, the direction of the stabbing) and the weapon’s possible characteristics by examining the stab wound. The determination of these characteristics can be made only with a high level of uncertainty, and the precise direction of the stabbing is often difficult to assess if only soft tissues are injured. Previously reported techniques used for the assessment of these wound characteristics have substantial limitations. This manuscript presents a method using today’s easily accessible three-dimensional (3D) printing technology for blade-wound comparison and wound track determination. Scanning and 3D printing of knives is a useful method to identify weapons and determine the precise stabbing direction in a stabbing incident without compromising the trace evidence or the autopsy results. Ballistic gel experiment, and dynamic stabbing test experiments prove the method can be applied in safety, without compromising the autopsy results. Identification of the exact knife is not possible with complete certainty but excluding certain knives will decrease the number of necessary DNA examinations, hence it can lower the burden on forensic genetic laboratories. The method addresses many of the shortcomings of previously used methods of probe insertion or post-mortem CT. Insertion of the printed knife into the wound gives a good visual demonstration of the stabbing direction, thus easing the forensic reconstruction of the stabbing incident. After combining the 3D printing with photogrammetry, the achieved 3D visualization is useful for courtroom demonstration and educational purposes.

Variability and specificity of bone cutting mark properties in cases involving stabbing with knives

Sharp force traumas are frequently encountered in stabbing crime victims. During an examination, the properties of cutting marks in bones are compared with the properties of suspect tools, particularly knives. Therefore, the variation and specificity of knife and cutting mark properties must be known. This article provides the variability and specificity of a set of knife blade and cutting mark properties. Plain and serrated knives are used to create experimental cutting marks in porcine ribs, knife properties are derived from surface acquisitions of the blades and mark properties from Micro-CT data. We consider two conditions, automated stabbing using a motorized stage and manual stabbing. In addition, we study the influence of maceration on marks. For knives, the blade edge angle, blade thickness, and bevel height, and for cutting marks, the shape, the wall angle, the width, and the bevel height are determined and compared. The results show that the relationship between corresponding properties of blades and marks depends on the knife type. For plain knives, the width and wall angle of the marks are dependent on the mark depth and are significantly smaller than the blade properties edge angle and width. For serrated knives, this is not the case. The mark shape only provides slight support for a knife type for marks deeper than the blade bevel height. In conclusion, mark properties are only specific for a particular knife brand and model if the blade properties differ significantly and assuming a specific knife type.

Knife cut marks inflicted by different blade types and the changes induced by heat: a dimensional and morphological study

Detailed information on skeletal trauma analysis of burned bone is important to ascertain the manner and cause of death in forensic casework. This research used three different knife types, one with a non-serrated blade, one a fine-serrated blade, and one a coarse-serrated blade, to inflict trauma to manually macerated Sus scrofa ribs (n = 240), and these ribs were later exposed to heat. Qualitative and quantitative analyses were conducted using macroscopic and microscopic techniques to assess specific characteristics of the cut marks. Differences in cut mark dimension and morphology of the ribs were investigated. After heat exposure, the cut marks on the rib samples remained recognisable and did not alter considerably. A level of dimensional and morphological preservation was reliant on the cutting action and the features of the knife blade as well as surrounding bone injury. The cut marks inflicted by the non-serrated blade remained recognisable despite exposure to the burning process. However, the cut marks inflicted by the coarse-serrated blade were likely to change significantly when exposed to heat. This study leads to two important results: (1) identification of pre-existing cut marks prior to heat exposure is possible in reconstructed burned bone fragments, and (2) cut marks from different types of knife blades showed dissimilar responses to heat. The outcomes obtained in this study stressed the need to adopt great care with the effects of heat on skeletal trauma analysis.

Insights to enhance the examination of tool marks in human cartilage

This work deals with the examination of tool marks in human cartilage. We compared the effectiveness of several cleaning methods on cut marks in porcine cartilage. The method cleaning by multiple casts achieved the significantly highest scores (P = 0.02). Furthermore, we examined the grain-like elevations (dots) located on casts of cut cartilage. The results of this study suggest that the casting material forms these dots when penetrating cartilage cavities, which are areas where the strong collagen fibres leave space for the chondrocytes. We performed fixation experiments to avoid this, without success. In addition, 31 casting materials were compared regarding contrast under light-microscope and 3D tool marks scanner. Under the light-microscope, brown materials achieved significantly higher values than grey (P = 0.02) or black (P = 0.00) whereas under the 3D scanner, black materials reached higher contrast values than grey (P = 0.04) or brown (P = 0.047). To compare the accuracy and reproducibility of 6 test materials for cartilage, we used 10 knives to create cut marks that were subsequently scanned. During the alignment of the individual signals of each mark, the cross-correlation coefficients (X_max) and lags (L_Xmax) were calculated. The signals of the marks in agarose were aligned with significantly fewer lags and achieved significantly higher cross-correlation coefficients compared to all tested materials (both P = 0.00). Moreover, we determined the cross-correlation coefficients (X_C) for known-matches (KM) per material. Agarose achieved significantly higher values than AccuTrans®, Clear Ballistics™, and gelatine (all P = 0.00). The results of this work provide valuable insights for the forensic investigation of marks in human costal cartilage.

A histological comparison of non-human rib models suited for sharp force trauma analysis

Cut marks provide essential knowledge to interpret which and how tools were used, both in archaeological and forensic context. Lots of studies focused on experimentally produced cut marks on animal models to develop methods for stabbing incidents. However, animal models are criticized to be morphologically different in comparison to human bones. This study analyzed the bone composition and experimentally obtained cut marks done on ribs from humans, pigs and goats. Methods included a qualitative description of differences between the species and a quantitative analysis of the cut mark proportions in histological thin sections and micro CT scans. The results indicated that especially the cortical bone of non-human ribs was different in comparison to human bone tissue as they were more robust and usually juvenile. Plexiform bone dominates and remodeled lamellar bone is rarely visible. The knife impact tends to create debris inside the cut mark and stress fractures along lamellae and cement lines perpendicular to the cut mark. Moreover, entheses of the intercostal muscles are always affected by the incision. Pig ribs were shown to be better suited as a model for sharp force trauma than goat ribs in comparison to humans. Though, plexiform bone and non-remodeled bone made it not quite ideal. We suggested to use bone material from animals used for breeding instead of meat production as they are slaughtered at higher ages.

Sharp bone trauma diagnosis: a validation study using epifluorescence microscopy

Identifying tool mark and involved weapon in sharp force trauma is essential to understanding the circumstances of death. But accuracy and reliability of such expert testimony remains unknown, and validation studies are rare in forensic literature. That is why, we conducted an experiment in order to determine error rates and predictive values on identifying the right implement through different types of knife-inflicted trauma. Human bone cut marks were analysed through epifluorescence microscopy. The samples were examined through a randomised, blinded, controlled study by three researchers with varying degrees of experience with direct and indirect observation of cut marks (photography). Our results showed that identifying the weapon involved is possible thanks to numerous criteria analysis. Correct classification rates were high and misclassifications rare. Asymmetric blades obtained better results than symmetric blades. Predictive values were also calculated, and the negative one reached very high levels, near 100% with regard to all the implements. Positive predictive values were more variable. But even if individual diagnoses remain in doubt, triage can be done and tools not implicated in injury can be eliminated with certainty. Moreover, our work clearly highlighted the importance of experience in such activities. A high level of experience is fundamental to obtain the best values, especially in such a context where evidence reliability is extremely important for forensic admissibility testimony in the court.

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.

Skeletal Trauma: An Anthropological Review

As anthropologists take on a larger role in medical examiner's offices, the incorporation of bone trauma analysis into the autopsy increases. The purpose of this invited review is to summarize recent anthropological literature that exemplifies the value of forensic anthropology in medicolegal death investigation, concentrating in the area of skeletal trauma analysis. Forensic anthropologists have a strong understanding of bone's response to trauma, gained through research and case studies. With this body of knowledge they are able to examine and interpret skeletal injury resulting from blunt, sharp, firearm, and thermal trauma. For example, toolmark class characteristics are recognized through sharp force injury examination, and fracture pattern analysis provides details of the impacting surface area. Interpretation of skeletal trauma allows for reconstruction of events surrounding death, and may inform the manner of death classification.

Forensic Veterinary Pathology

Sharp-force injuries are injuries caused by a mechanical force using sharp objects against the skin. Sharp-force injuries are mainly classified as stab, incised, chop, and therapeutic wounds and are less frequent than blunt-force injuries in animals. The analysis of the edges of the wound is crucial, especially if more than one type of lesion is involved. It may be difficult to differentiate between sharp trauma and blunt trauma, because lacerations can resemble incised wounds. The accurate documentation and examination of these injuries may indicate the instrument involved, the relationship between the animal and the perpetrator, and the force of the stab. Situations in which this type of trauma occurs may involve social violence, accidents, hunting, veterinary medical management, and religious rituals. The causes of death related to this type of trauma include hypovolemic shock, pneumothorax, or asphyxiation due to aspiration of blood. Necropsy findings should provide objective and unbiased information about the cause and manner of death to aid the investigation and further judgment of a possible crime.

Modeling and determination of directionality of the kerf in epifluorescence sharp bone trauma analysis

Characteristics of sharp bone trauma can be extremely useful to determine the origin of cut marks and to provide information regarding the context of death. Using human ribs and clavicle bones, this study analyzes the characteristics of bone kerfs made by different bladed implements, thanks to epifluorescence macroscopy. This technique, which is a nondestructive tool that uses autofluorescence of bones, documents bone damage precisely with high resolution. Both qualitative and quantitative criteria are analyzed. Our results identify unique class characteristics on bone lesions, allowing modeling kerf depending on the weapon, regardless of the type of bone that is wounded. Moreover, we demonstrate for the first time microscopic criteria of directionality, using fluorescence excitation. Orientation of cracks, flakes, and lateral pushing back especially helps in determining the tip and the end of the lesion, leading to the position of the aggressor. Kerf wall characteristics and striation location are also very useful. Epifluorescence macroscopy could be a new tool of choice in anthropology through cut mark analysis in establishing how the blade was used and providing details about the blow.