Microscopic analysis of cut mark characteristics from chopping/hacking tools.

Evaluating sharp force trauma (SFT) injuries to bone inflicted by a larger class of chopping/hacking tools (i.e., swords, axes, hatchets, machetes, and cleavers) is a growing area within the field of forensics. Previous studies have demonstrated promise regarding tool differentiation through the utilization of microscopic cut mark characteristics. However, this is an area that warrants additional investigation as there has yet to be a comprehensive study that incorporates the majority of these microscopic chopping/hacking cut mark characteristics into one analysis. The purpose of the current research was to analyze a large sample of microscopic cut mark characteristics derived from the current chopping/hacking literature to determine if differentiation of tool type could be made based on the microscopic cut mark characteristics. An additional goal of the current research is to develop standardization guidelines for the assessment of cut marks, focusing on a comprehensive suite of microscopic cut mark characteristics commonly observed in the existing literature. The skeletal sample for the current research was derived from a previous macroscopic cut mark characteristic experiment where trauma was inflicted to 20 partially fleshed domestic pig (Sus scrofa domesticus) limbs utilizing four chopping/hacking tools (i.e., axe, hatchet, machete, and cleaver) as well as a large carving knife for comparison. Cut marks were evaluated for 15 microscopic cut mark characteristics to assess statistical significance. Utilizing a chi-square analysis, nine of the 15 microscopic cut mark characteristics demonstrated statistically significant differences in relation to the tool utilized, indicating moderate to relatively strong effect sizes. For example, it should be possible to use a combination of microscopic cut mark characteristics to potentially indicate which chopping/hacking tool inflicted trauma when analyzing bones. In particular, examining the characteristics such as regularity of the cut mark edges along with the occurrence of uprising, fossae/depressions, and microscopic fractures can suggest or exclude tool class within forensic contexts.

A proposal for cut marks classification using machine learning: Serrated vs. non-serrated, single vs. double-beveled knives.

In tool mark identification, there is still a lack of characteristics and methodologies standardization used to analyze and describe sharp force trauma marks on skeletal remains. This study presents a classification method for cut marks on human bones, providing an applicable methodology for their examination and the relevant terminology for describing cases of sharp force trauma. A total of 350 cut marks were produced by stabbing pig ribs (Sus scrofa) with seven knives. The samples were analyzed under a stereomicroscope with a tangential light source. Through the analysis of cut marks, eleven traits were identified as significantly associated with the type of knife used. These traits included the general morphology of the kerf shape, the entrance and exit cross-profile shapes, the location of the rising on the entrance and exit cross-profile, the presence or absence of feathering, the presence or absence of shards and the location and the general morphology of the mounding. Binary logistic regression models were later trained and tested using nine out of the eleven traits. The first model categorized the cut mark as either produced by a serrated or non-serrated blade, while the second, as either produced by a single- or double-beveled blade. Classification scores of those models ranged between 63%-85% for the serration class and 63%-89% for the blade bevel class. This study proposes a new set of traits and the use of machine learning models to standardize and facilitate the analysis of stab wounds.

Fracture variation in survivable versus fatal blunt force trauma associated with intimate partner violence.

Intimate partner violence (IPV) is a global human rights issue that affects approximately 25% of women and 10% of men and is the leading cause of homicides of women worldwide. Multiple interventional studies have been conducted to screen for IPV; however, fractures associated with intimate partner homicide (IPH) have not been studied from a forensic anthropological perspective. Therefore, this study uses computed tomography scans of IPH victims (n=33) obtained from the New Mexico Office of the Medical Investigator to 1) classify and quantify perimortem craniofacial blunt force fractures, and 2) compare the IPH-related fractures to those associated with non-lethal IPV using previously published studies. The results indicate that IPH cases presented similarly to non-lethal IPV cases in that they were concentrated on the middle and lower face, but fractures were more frequent in the upper face and cranial vault in IPH cases. While IPH cases showed more fractures, they were not necessarily associated with extensive fracturing, as 75.8% of IPH victims had five or fewer fractures-the most common being comminuted and linear fractures, comprising 93.8% of IPH-related fractures. As IPV is significantly underreported, understanding the nuances of fracture patterns associated with IPH can help to aid holistic forensic investigations.

Effects of kinetic energy and firearm-to-target distance on fracture behavior in flat bones.

This research implements a fractographic approach to investigate the relationships between kinetic energy, firearm-to-target distance, and various aspects of fracture behavior in gunshot trauma. Gunshot experiments were performed on pig scapulae (n = 30) using three firearms generating different muzzle (initial) kinetic energies, including a 0.32 pistol (103 J), 0.40 pistol (492 J), and 0.308 rifle (2275 J). Specimens were shot from two distances: 10 cm (n = 15) and 110 cm (n = 15). Features evaluated in fractographic analysis such as cone cracks, radiating cracks, crack branching points, and circumferential cracks could be easily identified and measured in flat bones and allowed for statistical comparison of crack propagation behavior under different impact conditions. Higher-energy bullets produced more radiating cracks, more crack branching points, and longer fracture lengths than lower-energy bullets. Distance had no significant effect on fracture morphology at the distances tested. That quantitative measures of crack propagation varied with energy affirms that kinetic energy transfer is important in determining the nature and extent of fracture in gunshot wounds and suggests it may be possible to infer relatively high- versus relatively low-energy transfer using these features. Ranges obtained with the three firearms exhibited considerable overlap, however, indicating that other variables such as bullet caliber, mass, and construction influence the efficiency of energy transfer from bullet to bone. Therefore, fracture morphology cannot be used to identify a specific firearm or to directly reconstruct the muzzle (initial) kinetic energy in forensic cases.

Effects of input energy and impactor shape on cranial fracture patterns.

This study documents relationships between input energy, impactor shape, and the formation of fractures in human crania. Parietal impact experiments (n = 12) were performed at 67% higher input energy compared to previously reported experiments. Fracture origins, characteristics, and locations were compared at two input energy levels with three impactor shapes (focal "hammer", flat "brick", and curved "bat"). Impacts with all three impactors at both energy levels produced fractures originating at and remote to the impact site, indicating both mechanisms are typical in temporoparietal blunt force impacts. Higher energy impacts generally produced more impact site fractures, depression, and comminution than lower energy impacts. A small, focal impactor produced cone cracks, depression, and fractures localized near the impact site. A broad, curved impactor produced circumferential fractures and linear fractures extending into adjacent bones. A broad, flat impactor produced fracture patterns ranging from linear fractures to large depressed and comminuted defects.

Analysis of skeletal trauma on the bodies found in a mass grave.

This study was based on the data from the casefiles of the Institute of Forensic Medicine (IFM) in Kosovo, to analyse and interpret trauma observed on individuals recovered from a mass grave in Rudnica, Serbia. The intention was to determine if there is a pattern of trauma characteristic of this mass grave that informs about the manner of death and whether this is consistent with witness testimonies. The study considers the limitations of such analysis and interpretation, with special consideration of the completeness of the remains. The casefiles of 54 individuals recovered from the Rudnica mass grave from April to June 2014 were examined. A descriptive analysis was undertaken of the demographic profile of the sample, primary site of burial, completeness of the bodies, type and distribution of trauma, and the documented cause of death. All the individuals identified from the Rudnica mass grave were male aged from 14 to 96 years at time of death originating from four separate primary events with two known primary burial sites. Overall, 56% of the bodies were almost complete, 35% incomplete, and 9% complete. Discussion of the determination of completeness is included herein. The only type of trauma documented on the remains was gunshot wound trauma with the distribution of injuries concentrated on the trunk, followed by the limbs and head/neck regions. The cause of death was established in 56% of the cases. A pattern of trauma on the skeletal remains from the Rudnica mass grave was established based on the distribution and type of trauma documented from the dataset of each individual. These findings can be used as a basis for future studies in this field of research by taking a similar approach on larger samples and addressing the limitations encountered here.

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.

Investigating reverse butterfly fractures: An experimental approach and application of fractography.

Butterfly fractures are expected to form with the transverse portion on the tension side and the wedge portion on the compression side of a bent bone, however wedges have also been observed in the reverse orientation and are reported to be frequent in concentrated 4-point bending. To investigate how these fractures form, concentrated 4-point bending experiments were performed on nine human femora and documented using high-speed video. Videos showed the wedge portion formed as fracture initiated in tension, branched obliquely, then curved to terminate on the tension face. The transverse portion formed as a crack traveled between the curved fracture branch and the compression face. Fractography was also applied to evaluate fracture surfaces. At least one fractography feature was present in all femora and 32/35 bone fragments examined. Fracture propagation sequences interpreted using fractography matched those observed on video, demonstrating the utility of this method for evaluating complex fracture patterns.

A multidisciplinary investigation of chronic animal abuse: Collaboration between veterinary forensics and forensic anthropology.

An unknown juvenile female mixed breed dog was found non-ambulatory on a dead-end street in an urban setting adjacent to a public park. During initial veterinary examination, she was assessed to have untreatable injuries and was humanely euthanized. The forensic veterinarian requested consultation from a forensic anthropologist to assist with documenting antemortem skeletal trauma. Analyses of skeletal tissues indicated numerous injuries in various stages of healing diagnostic of non-accidental injuries. Veterinary forensic cases may benefit from collaborative analysis of bony remains by forensic anthropologists.

An assessment of the reliability of cut surface characteristics to distinguish between hand-powered reciprocating saw blades in cases of experimental dismemberment.

Criminal dismemberment is most commonly committed with a variety of hand-powered saws. These saws leave characteristic marks upon the bone that can assist in the identification of the weapon utilized. The current study provides frequencies of presentation of ten cut surface characteristics and examines intra- and interindividual variation between three hand-powered reciprocating saws. Pig radii were used as a proxy for human remains. 42 cut surfaces were created with three hand-powered reciprocating saws by the same researcher. Cut surface characteristics were assessed macroscopically, microscopically and with Scanning Electron Microscope (SEM), as well as photographed with Reflectance Transformation Imaging (RTI). Cut surface polish is the only characteristic that demonstrates consistently significant difference between saws. Five characteristics demonstrate some variation between blades: entrance shaving, breakaway spurs, breakaway notches, pull-out striae, and tooth hop. Four characteristics demonstrate no difference between blades: cut surface striation shape, cut surface striation regularity, harmonics, and exit chipping. Tooth hop is the most reliable characteristic for differentiating between blades in this study, while pull-out striae demonstrates high intra-individual variability and a low frequency of presentation making it unreliable for differentiating between saw blades. Cut surface striations, exit chipping, and breakaway spurs occurred with the highest frequencies and were reliable for determining direction of blade progress and blade stroke, but were not reliable for differentiating between saw blades. Harmonics were absent. Further research is necessary to create large databases of known saw mark examples with known intra- and interindividual variability rates and error rates.

Examination of Hacking and Blunt Force Skeletal Trauma.

Hacking trauma is prevalent in forensic cases involving genocide and dismemberment, but research into the identification of this type of trauma is lacking. The present study examines characteristics of hacking and blunt force skeletal trauma in order to determine if there is a point at which blunt force trauma becomes distinguishable from hacking trauma. Ten implements with a range of blade angles (i.e., the striking surface of the implement) were used in conjunction with a controlled-force hacking device to impact 100 limb bones of white-tailed deer (Odocoileus virginianus). Observations of the trauma included the occurrence and degree of fragmentation, the entrance widths of the impacts, and composite scores of six hacking characteristics, especially the distinctive V-shaped kerf. ANOVA tests and regression analyses were used to assess the relationships between these characteristics and the blade angles. A significant relationship (p-value = 0.011) was found between the composite hacking scores and the blade angles, indicating that blunt force and hacking trauma can be distinguished. The entrance widths of the impacts exhibited a significant relationship with the blade angles (p-value = 0.037). There was also a significant relationship between the visibility of a V-shaped kerf in the bones (p-value = 0.003), with visibility decreasing around the 60° blade angle. These data should assist in establishing guidelines to differentiate hacking and blunt force skeletal trauma in cases where the implement is on a spectrum between sharp and blunt.

Experimental investigation of cranial fracture initiation in blunt human head impacts.

The relationship between the point of blunt impact and the location of cranial fracture initiation continues to be poorly understood. The current study used high-speed video to capture cranial fracture initiation and propagation in impact experiments on twelve unembalmed, intact human cadaver heads. Video footage provided direct evidence that blunt cranial impacts can produce linear fractures initiating peripheral to the impact site. Four tests produced only remote peripheral linear fractures with no damage at the known point of impact, demonstrating that the pattern of linear fractures does not necessarily indicate impact site. The range of variation observed in these experiments suggests that cranial fracture formation is more complex than it is typically described in the current literature. Differences in biomechanical and fracture results obtained with three different shaped implements provided evidence that impact surface is one important factor influencing the outcomes of blunt cranial impacts.

Assessing Impact Direction in 3-point Bending of Human Femora: Incomplete Butterfly Fractures and Fracture Surfaces,.

Current literature associates bending failure with butterfly fracture, in which fracture initiates transversely at the tensile surface of a bent bone and branches as it propagates toward the impact surface. The orientation of the resulting wedge fragment is often considered diagnostic of impact direction. However, experimental studies indicate bending does not always produce complete butterfly fractures or produces wedge fragments variably in tension or compression, precluding their use in interpreting directionality. This study reports results of experimental 3-point bending tests on thirteen unembalmed human femora. Complete fracture patterns varied following bending failure, but incomplete fractures and fracture surface characteristics were observed in all impacted specimens. A flat, billowy fracture surface was observed in tension, while jagged, angular peaks were observed in compression. Impact direction was accurately reconstructed using incomplete tension wedge butterfly fractures and tension and compression fracture surface criteria in all thirteen specimens.

An Examination of the Transition of Fracture Characteristics in Long Bones from Fresh to Dry in Central Florida: Evaluating the Timing of Injury.

It is important to conduct timing of injury research analyzing fracture characteristics at known postmortem intervals (PMI) because bone can retain fresh characteristics throughout the PMI. Defleshed pig (Sus scrofa) long bones were fractured weekly in two environments (full sun and shade) over 14 weeks in Central Florida and fracture characteristics were categorized (N = 136) for analysis. Results of analysis of variance (ANOVA) using time in weeks (PMI) as a dependent variable indicate significant relationships between PMI and Fracture Angle (p < 0.001), Fracture Surface (p < 0.001), and Fracture Outline (p < 0.001). Fracture characteristics associated with perimortem trauma (smooth Fracture Surfaces and curved or V-shaped Fracture Outlines) were commonly observed. Analysis of fracture characteristics for each environment demonstrated similar patterns. Overall, the loss of only fresh fracture characteristics for each bone was noted earlier in the PMI for the Central Florida region than previously reported.

Chronic alcoholism and bone remodeling processes: Caveats and considerations for the forensic anthropologist.

Clinical literature provides substantial information on the effects of chronic alcohol abuse on bone remodeling and related skeletal disease processes. This biomedical information is seldom considered in detail by forensic anthropologists, who often rely on normative macroscopic models of bone remodeling and traditional macroscopic age estimation methods in the creation of biological profiles. The case study presented here considers the ways that alcoholism disrupts normal bone remodeling processes, thus skewing estimations of age-at-death. Alcoholism affects bone macroscopically, resulting in a porous appearance and an older estimation of age, while simultaneously inhibiting osteoblastic activity and resulting in a younger microscopic appearance. Forensic anthropologists must also be cognizant of pathological remodeling stemming from alcoholism in cases where trauma analysis is critical to the reconstruction of events leading up to death, as fracture healing rates can be affected. Beyond the case study, we also consider how forensic anthropologists and practitioners can recognize and account for osteological signatures of alcoholism in medico-legal contexts. In order to best estimate age at death, a combined macroscopic and microscopic approach should be employed whenever possible alcohol and drug abuse is known or suspected.

The Utility of Forensic Anthropology in the Medical Examiner's Office.

Over the past few decades, the field of forensic anthropology has seen major advancements and experienced a considerable growth of professionals in medical examiner/coroner offices. Despite this expansion, misconceptions regarding the role and utility of the anthropologist in the medicolegal setting still exist. This article brings together practitioners employed full-time in four medical examiner's offices, with each practitioner providing a unique perspective and emphasis regarding their role as an anthropologist. Discussed is the history of the anthropology division in each office as well as the types of casework and ancillary duties completed by the anthropologists. Consistently, the anthropologists are involved in the search and recovery of human remains, managing long-term unidentified cases, facilitating disposition of unclaimed decedents, and developing mass disaster protocols for their respective agency. Also consistent across the four offices is the fact that the anthropologists receive far more consult requests for trauma evaluation of nonskeletonized cases than any other type of case.

Classification of pelvic ring fractures in skeletonized human remains.

Pelvic ring fractures are associated with high rates of mortality and thus can provide key information about circumstances surrounding death. These injuries can be particularly informative in skeletonized remains, yet difficult to diagnose and interpret. This study adapted a clinical system of classifying pelvic ring fractures according to their resultant degree of pelvic stability for application to gross human skeletal remains. The modified Tile criteria were applied to the skeletal remains of 22 individuals from the Cleveland Museum of Natural History and Universidad Nacional Autónoma de México that displayed evidence of pelvic injury. Because these categories are tied directly to clinical assessments concerning the severity and treatment of injuries, this approach can aid in the identification of manner and cause of death, as well as interpretations of possible mechanisms of injury, such as those typical in car-to-pedestrian and motor vehicle accidents.