While assessing skeletal injuries in human skeletal remains, forensic anthropologists are frequently presented with fractured, fragmented, or otherwise modified skeletal remains. The examination of evidence and the mechanisms of skeletal injuries often require that separate osseous elements be permanently or temporarily reassembled or reconstructed. If not dealt with properly, such reconstructions may impede accurate interpretation of the evidence. Nowadays, routine forensic examinations increasingly incorporate digital imaging technologies. As a result, a variety of PC-assisted imaging techniques, collectively referred to as the virtual approach, have been made available to treat fragmentary skeletal remains. The present study employs a 3D virtual approach to assess mechanisms of skeletal injuries, and provides an expert opinion of causative tools in three forensic cases involving human skeletal remains where integrity was compromised by multiple peri- or postmortem alterations resulting in fragmentation and/or incompleteness. Three fragmentary skulls and an incomplete set of foot bones with evidence of perimortem fractures (gunshot wounds) and sharp force trauma (saw marks) were digitized using a desktop laser scanner. The digitized skeletal elements were reassembled in the virtual workspace using functionalities incorporated in AMIRA® version 5.0 software, and simultaneously in real physical space by traditional reconstructive approaches. For this study, the original skeletal fragments were substituted by replicas built by 3D printing. Inter-method differences were quantified by mesh-based comparison after the physically reassembled elements had been re-digitized. Observed differences were further reinforced by visualizing local variations using colormaps and other advanced 3D visualization techniques. In addition, intra-operator and inter-operator error was computed. The results demonstrate that the importance of incorporating the virtual approach into the assessment of skeletal injuries increases with the complexity and state of preservation of a forensic case. While in relatively simple cases the virtual approach is a welcome extension to a traditional approach, which merely facilitates the analysis, in more complex and extensively fragmentary cases such as multiple gunshot wounds or dismemberment, the virtual approach can be a crucial step in applying the principles of gunshot wounds or sharp force traumatic mechanisms. The unrestricted manipulation with digital elements enabling limitless repairs and adjustments to a "best-case scenario" also produced smaller inter-operator variation in comparison to the traditional approach.

Department of Biological Sciences North Carolina State University Campus Box 7614 Raleigh NC 27695 7614 United States of America

Laboratory of Morphology and Forensic Anthropology Department of Anthropology Faculty of Science Masaryk University Kotlářská 2 611 37 Brno Czech Republic

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