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.

Identification of a decedent in a 103-year-old homicide case using forensic anthropology and genetic genealogy.

Anthropologists are often the custodians of long-term unidentified human remains though their positions as curators of university or museum skeletal collections. Various factors decrease the solvability of these legacy cases including the passage of time, the loss of provenience for specific cases, and lack of documentation or case records. While anthropologists can contribute important information toward identification, it is often necessary to explore novel and cross-disciplinary strategies to resolve difficult cold cases. In long cold cases, the postmortem interval, in particular, may be difficult to estimate leading to further challenges in achieving identification. Modern advances in radiocarbon bomb pulse dating, isotope analysis, and actualistic studies have contributed to positive identification of unidentified human remains in some legacy cases, but may not be available to all forensic practitioners and law enforcement from resource-poor agencies. Pooling resources, as well as collaborating with professionals outside of forensic anthropology, is a useful strategy to pursue when anthropological methods are exhausted.The case study presented here demonstrates a collaborative approach between forensic anthropologists, forensic genetic genealogists, and law enforcement in a century-old homicide. The dismembered and mummified parts of a male body were recovered in a remote cave in 1979 and again in 1991. Despite forensic anthropologists creating and updating the biological profile over the decades from recovery to present, no identification was made until the application of forensic genetic genealogy (FGG) to the case in 2019. New interpretations of bone microstructure and trauma analysis are presented for the case, alongside the historical documentation and "proof of life" evidence used by the genealogy team. A review of the FGG methods underscores the challenges in this case (e.g. significant endogamy, multiple aliases used by the victim) and the steps taken toward resolution. Ultimately, a combined anthropology and genealogy approach resulted in a confirmed identity for a man who was murdered in 1916.Key pointsForensic scientists should leverage a collaborative, interdisciplinary approach toward human identification.When combined with forensic anthropology methods, forensic genetic genealogy is a valuable tool linking biological and cultural-historical aspects of identity.Forensic anthropologists should review challenging cases in their labs as new methods are introduced and new resources become available.

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.

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.

Application of the Stephan et al. Chest Radiograph Comparison Method to Decomposed Human Remains.

This manuscript describes the use of comparative radiography of the chest to facilitate positive identification of human remains in advanced stages of decomposition. The method reported by Stephan et al. for positive identification of dry, disarticulated skeletal elements was used on semifleshed, decomposing remains. Positive identification was established through multiple points of concordance observed in radiographs of the left and right clavicles and the C5-T1 vertebrae. This case study demonstrates the applicability of the Stephan et al.'s method in cases involving decomposing remains.