The virtual approach to the assessment of skeletal injuries in human skeletal remains of forensic importance

Utilizing augmented reality for reconstruction of fractured, fragmented and damaged craniofacial remains in forensic anthropology

Forensic anthropologists are often confronted with human remains that have been damaged due to trauma, fire, or postmortem taphonomic alteration, frequently resulting in the fracture and fragmentation of skeletal elements. The augmented reality (AR) technology introduced in this paper builds on familiar 3D visualization methods and utilizes them to make three dimensional holographic meshes of skeletal fragments that can be manipulated, tagged, and examined by the user. Here, CT scans, neural radiance fields (NeRF) artificial intelligence software, and Unreal Engine production software are utilized to construct a three-dimensional holographic image that can be manipulated with HoloLens™ technology to analyze the fracture margin and reconstruct craniofacial elements without causing damage to fragile remains via excessive handling. This allows forensic anthropologists a means of assessing aspects of the biological profile and traumatic injuries without risking further damage to the skeleton. It can also be utilized by students and professional anthropologists to practice refitting before reconstructing craniofacial fragments if refitting is necessary. Additionally, the holographic images can be used to explain complicated concepts in a courtroom without the emotional response related to using bony elements as courtroom exhibits.

Title: Skeletal evidence of the ethnic cleansing actions in the Free City of Danzig (1939-1942) based on the KL Stutthof victims analysis

In the early days of World War II, many of the prominent and influential people of Polish nationality from the Free City of Danzig were arrested by the Germans and sent to the nearby concentration camp KL Stutthof. Nearly a hundred of them died within the next seven months upon their arrival, and were buried in a clandestine mass grave in a nearby forest. However, the exact nature of their death is unknown, as it is unclear what the attitude of the aggressors was toward the victims. We do not know whether there was only one executioner or there were several assassins, nor if the killing methodology was consistent with the other state-regulated executions. The studied material represents the commingled remains of a minimum thirty-four people, possibly all male, aged from under eighteen to over sixty at the time of death. Perimortem traumatic lesions are shown mainly on the skull bones. We asked whether the perimortem trauma lesions visible on the victims' skeletons could be informative on the cause and manner of their death. Our results show the prevalence of the perimortem trauma inflicted by a blunt object are on the parietal bones above the Hat Brim Line (HBL), which is commonly associated with a violent attack. The gunshot trauma was usually localized on the occipital bone or posterior parietal, which could indicate a shot to the back of the head, and this was commonly encountered during executions. No signs of defensive injuries can be explained either by restraining of the hands or by a surprise attack. The abundance and variability of the trauma type can be evident of multiple assailants. Moreover, the multiple impact points detected on several crania prove unnecessary overkill and brutality, which reflects the personal attitudes of the executioners towards the victims.

Use of Different Digitization Methods for the Analysis of Cut Marks on the Oldest Bone Found in Brittany (France)

Archaeological 3D digitization of skeletal elements is an essential aspect of the discipline. Objectives are various: archiving of data (especially before destructive sampling for biomolecular studies for example), study or for pedagogical purposes to allow their manipulation. As techniques are rapidly evolving, the question that arises is the use of appropriate methods to answer the different questions and guarantee sufficient quality of information. The combined use of different 3D technologies for the study of a single Mesolithic bone fragment from Brittany (France) is here an opportunity to compare different 3D digitization methods. This oldest human bone of Brittany, a clavicle constituted of two pieces, was dug up from the mesolithic shell midden of Beg-er-Vil in Quiberon and dated from ca. 8200 to 8000 years BP. They are bound to post-mortem processing, realized on fresh bone in order to remove the integuments, which it is necessary to better qualify. The clavicle was studied through a process that combines advanced 3D image acquisition, 3D processing, and 3D printing with the goal to provide relevant support for the experts involved in the work. The bones were first studied with a metallographic microscopy, scanned with a CT scan, and digitized with photogrammetry in order to get a high quality textured model. The CT scan appeared to be insufficient for a detailed analysis; the study was thus completed with a µ-CT providing a very accurate 3D model of the bone. Several 3D-printed copies of the collarbone were produced in order to support knowledge sharing between the experts involved in the study. The 3D models generated from µCT and photogrammetry were combined to provide an accurate and detailed 3D model. This model was used to study desquamation and the different cut marks, including their angle of attack. These cut marks were also studied with traditional binoculars and digital microscopy. This last technique allowed characterizing their type, revealing a probable meat cutting process with a flint tool. This work of crossed analyses allows us to document a fundamental patrimonial piece, and to ensure its preservation. Copies are also available for the regional museums.

The big puzzle: A critical review of virtual re-association methods for fragmented human remains in a DVI context'

During a Disaster Victims Identification (DVI) mission, international protocols rely on interdisciplinary work, especially between specialists from forensic imaging and anthropology. In case of air crashes or explosions, DVI units may face thousands of fragmented human remains (FHRs). The physical re-association of FHRs and the identification process is very complex and challenging, and relies upon expensive and destructive DNA analysis. A virtual re-association (VRA) of these fragments, using Multidetector Computed Tomography (MDCT), could be a helpful tool in forensic anthropology analysis, as it could assist in reducing the number of DNA samples. However, there is no standardized protocol for including such an approach into a DVI procedure. The aim of this study was to summarize and analyze existing techniques through a systematic review and to develop a protocol for virtual re-association of FHRs, adapted to the DVI context. A keyword-based literature search was conducted, focusing on the VRA methods using MDCT imaging and 3D surface scan methodology. Reviews and primary articles, published between 2005 and 2020 in the fields of forensic anthropology, paleoanthropology, archeology, and fracture reduction surgery were sorted out. A total of 45 publications were selected and analyzed based on their content and relevance. The results show that research on the re-association of FHRs increased significantly during the last five years. Seven steps regarding the MDCT-based method for the virtual re-association of FHRs could be identified: acquisition of 3D-images, segmentation of the MDCT-data, post-processing and surface generation, identification of intact and fracture surfaces, identification and registration of matching fragments, and validation of the re-association. The literature is surprisingly sparse regarding the FHRs re-association as a forensic tool, and mainly consists in case reports, whereas validated methods were presented in archeology and surgery publications. However, we were able to adapt the MDCT-based approach for the virtual re-association of the FHRs and propose an innovative protocol for DVI missions. This protocol includes the needed details, from the acquisition of MDCT imaging to the virtual re-association of 3D models and its validation. Each step has to be fully tested, adapted and validated in future studies.

Sex estimation in a Turkish population using Purkait’s triangle: a virtual approach by 3-dimensional computed tomography (3D-CT)

Sex estimation is considered one of the first steps in the forensic identification process. Morphological and morphometrical differences between males and females have been used as means for morphoscopic and metric methods on both cranial and postcranial skeletal elements. When dry skeletal elements are not available, virtual data can be used as a substitute. The present research explores 3-dimensional (3D) scans from a Turkish population to test a sex estimation method developed by Purkait (2005).

Overall, 296 individuals were used in this study (158 males and 138 females). Purkait’s triangle parameters were measured on computed tomography (CT) scans obtained from both right and left femora of each patient at the Bakirkoy Dr. Sadi Konuk Training Research Hospital (Istanbul, Turkey). Intra- and inter-observer errors were assessed for all variables through technical error of measurements analysis. Bilateral asymmetry and sex differences were evaluated using parametric and non-parametric statistical approaches. Univariate and multivariate discriminant function analyses were then conducted.

Observer errors demonstrated an overall agreement within and between experts, as indicated by technical error of measurement (TEM) results. No bilateral asymmetries were reported, and all parameters demonstrated a statistically significant difference between males and females. Fourteen discriminant models were generated by applying single and combined parameters, producing a total correct sex classification ranging from 78.4% to 92.6%. In addition, over 67% of the total sample was accurately classified, with 95% or greater posterior probabilities.

Our study demonstrates the feasibility of 3D sex estimation using Purkait’s triangle on a Turkish population, with accuracy rates comparable to those reported in other populations. This is the first attempt to apply this method on virtual data and although further validation and standardisation are recommended for its application on dry bone, this research constitutes a significant contribution to the development of population-specific standards when only virtual data are available.

Key points

CT analysis using Purkait’s triangle is a suitable tool for assessment of sex in unidentified individuals.

The best overall estimation rate was achieved with the F11 model, with around 92% of accuracy.

The results suggested 78.4% to 92.6% correct sex identification rates.

More research is needed to expand the sample set and verify the results.

Interpol review of shoe and tool marks 2016-2019

This review paper covers the forensic-relevant literature in shoe and tool mark examination from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

Digital restoration of fragmentary human skeletal remains: Testing the feasibility of virtual reality

Experts in forensic anthropology and medicine have become gradually accustomed to examining components of the human body in the virtual workspace. While the computer-assisted approach offers numerous benefits, the interactions with digital three-dimensional biological objects are often problematic, particularly if conducted with mouse, keyboard and flat-panel screen. The study focusses on feasibility of a virtual reality (VR) system for virtual restoration of fragmentary skeletal remains. The VR system was confronted with three cases of fragmentary remains. The cases were reassembled manually by twenty participants using a HTC Vive headset combined with an in-house application A.R.T. The same task was performed using a CloudCompare software in conjunction with a desktop peripheral. The two systems were compared in terms of time efficiency, the geometric properties of the resulting restorations, and convenience of use. Restoration using the VR system took approximately half the time the desktop set-up did. The VR system also yielded a lower error rate when a severely fragmented skull was reassembled. Ultimately, although the efficiency of the reassembling was shown to be strongly dependent on the operator's experience, the use of the VR system balanced out the uneven levels of proficiency in computer graphics. The current generation of virtual reality headsets has a strong potential to facilitate and improve tasks relating to the virtual restoration of fragmented skeletal remains. A VR system offers an intuitive digital working environment which is less affected by an operator's computer skills and practical understanding of the technology than the desktop systems are.

Using tibial fragments to reconstruct the total skeletal height of black South Africans

Stature is an important component of the biological profile of unknown skeletal remains and regression equations for estimating stature have been derived for a number of bones. However, bones are rarely recovered intact in both forensic and archaeological cases, and regression formulae for fragmentary remains have therefore been developed. These equations are, however, both sex- and population-specific, and while formulae exist for many populations, those using fragmentary tibiae do not exist for black South Africans. The aim of this study was therefore to establish regression equations for estimating total skeletal height (TSH), and thereby stature, from tibial fragments in a black South African population. A sample of 99 male and 99 female black South African skeletons were obtained from the Raymond A. Dart Collection of Human Skeletons and the TSH of each skeleton was calculated using the anatomical method. Eleven additional measurements representing tibial fragments were taken on each tibia, and both uni- and multivariate equations were established for estimating TSH from these fragments. All tibial variables were significantly, positively correlated with TSH, and equation correlations ranged between 0.41 and 0.91. The range of standard errors of estimate for the derived sex-specific (3.43-5.06 cm) and sex-pooled (3.44-5.94 cm) multivariate equations were slightly larger than those reported for intact tibiae in black (2.78-3.06 cm) and white (2.59-3.16 cm) South Africans. All uni- and multivariate-equations estimated TSH with moderate to high accuracy, which indicates that in the absence of intact tibiae, the equations presented in this study can be used to give accurate estimates of TSH, and thereby stature, for black South Africans.

Applying 3D prints to reconstructing postmortem craniofacial features damaged by devastating head injuries

Postmortem facial identification is one of the most common techniques for establishing a deceased person's identity. In victims suffering from devastating cranial injuries, the feasibility of facial identification tasks can be compromised by damage to or disfigurement of the identifying cranial features. Although there are several reconstructive approaches, which help experts to restore the essence of person's physical appearance, thus enhancing the chances of recognition, only a few of them involve restoring the fractured cranial bones as the foundation for the reconstructed soft tissues. Here, we propose a technique based on replacement of heavily damaged hard tissues with generic prosthetics manufactured by 3D printing. Our approach does not require medical imaging technologies or other costly lab equipment. It is simple, affordable and relatively labor-efficient. The deceased's reconstructed craniofacial features can be subsequently assessed, photographed, drawn or otherwise reproduced in order to help determine his or her identity. In addition, the imagery can be displayed, published or broadcasted in media without concerns of being overly graphic.