Virtual anthropology? Reliability of three-dimensional photogrammetry as a forensic anthropology measurement and documentation technique

Establishing the identity of unknown remains is a vital role of forensic anthropology. While establishing identity is generally straightforward due to conventional methods of identification like DNA analysis, sometimes these methods are not applicable in the case of remains that are heavily skeletonized, severely decomposed or severely charred. In such instances, a forensic anthropologist will be called upon. The role of the forensic anthropologist is to aid in the identification of remains when conventional methods such as DNA and fingerprinting are not applicable. They may also be required to collaborate with other experts like forensic odontologists in order to attain a positive identification. A number of methods are available to the anthropologist that can aid in achieving identification: comparative radiography, nonimaged records, craniofacial superimposition, dental comparison and craniofacial reconstruction. All the methods except nonimaged records require imaging, either in two dimensions or three dimensions. Three-dimensional imaging is quickly becoming a vital tool for reconstruction, comparison, and analysis in forensic science. It has found applications in road accident reconstruction, facial reconstruction, comparison of patterned injuries to the injury-inflicting instruments, and anthropometry. The main three-dimensional imaging methods utilized in the forensic field are photogrammetry, laser scanning and radiological scanning (computed tomography (CT) and magnetic resonance imaging (MRI)), with forensic three-dimensional/computer aided design (3D/CAD)-supported photogrammetry being the method that is primarily used due to its low cost, rapid results, does not need expertise to operate, has no radiation risks and, above all, the record is permanent. Regardless of this, CT and MRI are more established methods and are widely used in a variety of industries. The purpose of this paper is to compare and contrast the three-dimensional imaging methods currently employed in forensic science on the basis of reliability, reproducibility, and accuracy; with an ultimate aim of validating photogrammetry as an analytical and documentation method of forensic science

Virtual Anthropology: forensic applications to cranial skeletal remains from the Spanish Civil War

Biological and forensic anthropologists face limitations while studying skeletal remains altered by taphonomic alterations and perimortem trauma, such as in remains from the Spanish Civil War. However, virtual anthropology techniques can optimize the information inferred from fragmented and deformed remains by generating and restoring three-dimensional bone models. We applied a low-cost 3D modelling methodology based on photogrammetry to develop novel forensic applications of virtual 3D skull reconstruction, assembly, restoration and ancestry estimation. Crania and mandible fragments from five Spanish Civil War victims were reconstructed with high accuracy, and only one cranium could not be assembled due to extensive bone loss. Virtual mirroring successfully restored reconstructed crania, producing 3D models with reduced deformation and perimortem trauma. High correlation between traditional and virtual craniofacial measurements confirmed that 3D models are suitable for forensic applications. Craniometric databases of world-wide and Spanish populations were used to assess the potential of discriminant analysis to estimate population ancestry. Our protocol correctly estimated the continental origin of 86.7 % of 15 crania of known origin, and despite low morphological differentiation within European populations, correctly identified 54.5 % as Spanish and 27.3 % of them with high posterior probabilities. Two restored crania from the Civil War were estimated as Spanish, and one as a non-Spanish European. Results were not conclusive for one cranium and did not confirm previous archeological hypotheses. Overall, our research shows the potential to assess the presence of foreign volunteers in the Spanish Civil War and highlights the added value of 3D-virtual techniques in forensic anthropology

The frontal bone as a proxy for sex estimation in humans: a geometric morphometric analysis

Physical anthropologists have a toolkit for determining sex from skeletal remains composed of visual and metric techniques concerning the pelvis and the skull. However, complete elements are not always available and results can be indeterminate. The present study combines visual assessment of the skull with statistical methods of shape analysis, geometric morphometrics, to reach a better understanding of how cranial variation of the frontal bone is influenced by sex. The three-dimensional coordinates of frontal bone curvatures of 204 skulls from the Terry Collection were collected using a Microscribe digitizer. These data were used to assess the ability of this technique to estimate sex. Results of a Procrustes distance analysis of variance (ANOVA) suggest that variation in frontal bone curvature is explained best by sex compared to variables of ancestry and visual score. A discriminant function analysis (DFA) cross-validation test of sex classification showed the DFA correctly assigns frontal bones as female with 88.3% accuracy and males with 70.4% accuracy. These results suggest that this technique may be useful in future sex estimation software

Repeatability of a morphoscopic sex estimation technique for the mental eminence on micro-focus X-ray computed tomography models

Objectives Walker's sex estimation method is based on five morphoscopic features of the human skull. This study aimed at testing the repeatability of one of the five traits, the mental eminence, visually on three-dimensional (3D) models, compared to the traditional, tactile scoring approach on bone. Materials and methods The sample comprised 105 mandibles from the Pretoria Bone Collection and their respective virtual 3D models, obtained from micro-focus X-ray computed tomography (micro-XCT) scans. Four observers independently scored the bones first, followed by the virtual 3D modality. Intra- and interobserver errors (interOE and intraOE) were performed with Fleiss’ and Cohen's Kappa, respectively. We calculated the intermodality agreement per observer with Wilcoxon Signed-Rank tests. Results The intraOE was moderate on bone (κ=0.448) and substantial on 3D (κ=0.799), while the Fleiss’ Kappa test for the interOE resulted in slight agreement both on bone (κ=0.163) and 3D (κ=0.169) irrespective of level of experience. All Wilcoxon Signed-Rank test P-values were significant. Discussion and conclusion The application of the morphoscopic sex estimation for the mental eminence to micro-XCTs could be a matter of personal affinity as the level of experience did not play a role in the results. The expression of the mental eminence trait being population-specific, the individual's population affinity should be considered when sex is estimated in South African skeletons. It remains unclear whether the slight agreement between observers is due to the unreliability of the trait for sex estimation or whether the modalities are not easily interchangeable

South African cranial variation : a combined metric-macromorphoscopic method for ancestry estimation

Thesis (PhD (Anatomy))--University of Pretoria, 2023.Ancestry is a fundamental parameter of the biological profile. To date South African forensic anthropologists are only able to successfully apply a metric approach to estimate ancestry from skeletal remains. While a non-metric, or macromorphoscopic (MMS) approach exists, limited research has been conducted to explore its use in a South African population. The method has not been sufficiently tested and validated which is required for anthropological methodology to be compliant with standards of best practice. This study aimed to explore the MMS traits and its covariation with cranial measurements to develop improved methodology for the estimation of ancestry from skeletal remains in South Africa. A suite of 17 MMS traits and 25 standard linear measurements were collected from 660 crania of black, white and coloured South Africans. Inter- and intra-observer agreement was closely scrutinized as visual methods have been shown to be prone to error. The intra-observer agreement ranged from moderate to perfect, with three traits (inferior nasal margin, nasal bone shape, and nasal overgrowth) yielding slightly lower repeatability. Inter-observer agreement was assessed among five individuals with varying levels of general experience and familiarity with the traits. Overall, the observers demonstrated poor to substantial agreement. A group discussion on the scoring procedure, followed by subsequent rescoring of the crania showed a slight increase in overall agreement, with kappa values ranging between moderate and substantial. While general experience does not appear to translate to proficiency with the method, familiarity with the traits and scoring procedure contributes to consistent scores. Thus, method-specific training is essential prior to employing the MMS traits in practice. Technical error of measurement was used to assess the repeatability of the measurements, where the intra-observer error was noted to be lower than the inter-observer error. The greatest disparity was observed with the inter-orbital breadth and mastoid height for both the inter- and intra-observer assessments. The MMS trait frequency distributions revealed substantial group variation and overlap. Ultimately, not a single trait can be considered characteristic of any one population group. Kruskal-Wallis and Dunn’s tests demonstrated significant population differences for 13 of the 17 traits. Black and coloured South Africans, and coloured and white South Africans shared similarities for many of the traits, but black and white South Africans did not present with significant overlap for any trait. ANOVA and Tukey’s honestly significant difference (HSD) test revealed that all measurements were significantly different for ancestry, except the foramen magnum length. Substantial variation and overlap were observed for the measurements among all three groups. Random Forest Modelling (RFM) was used to develop classification models to assess the reliability and accuracy of the variables in identifying ancestry. Models were created for the traits and measurements separately to gauge the discriminatory power of each dataset. A combined model including all data was also created to test if mixed data can better capture cranial variation than individual methods. The MMS model outperformed the metric model, with classification accuracies of 79% and 72%, respectively. Ultimately, the best results were obtained with the mixed model, which yielded an accuracy of 81%. The results indicate that the combination of size and shape data (as quantified with the mixed model) can effectively distinguish between black, white and coloured South Africans despite significant group overlap. Thus, this study has shown the MMS traits to be a valid and tested method, and the population-specific data from this study can be used to add MMS analyses to forensic casework and skeletal analyses in South Africa.AnatomyPhD (Anatomy)UnrestrictedFaculty of Health SciencesSDG-16: Peace, justice and strong institution

On the persistence of race:Unique skulls and average tissue depths in the practice of forensic craniofacial depiction

The (re-)surfacing of race in forensic practices has received plenty of attention from STS scholars, especially in connection with modern forensic genetic technologies. In this article, I describe the making of facial depictions based on the skulls of unknown deceased individuals. Based on ethnographic research in the field of craniofacial identification and forensic art, I present a material-semiotic analysis of how race comes to matter in the face-making process. The analysis sheds light on how race as a translation device enables oscillation between the individual skull and population data, and allows for slippage between categories that otherwise do not neatly map on to one another. The subsuming logic of race is ingrained – in that it sits at the bases of standard choices and tools – in methods and technologies. However, the skull does not easily let itself be reduced to a racial type. Moreover, the careful efforts of practitioners to articulate the individual characteristics of each skull provide clues for how similarities and differences can be done without the effect of producing race. Such methods value the skull itself as an object of interest, rather than treat it as a vehicle for practicing race science. I argue that efforts to undo the persistence of race in forensic anthropology should focus critical attention on the socio-material configuration of methods and technologies, including data practices and reference standards.<br/

A Survey on Artificial Intelligence Techniques for Biomedical Image Analysis in Skeleton-Based Forensic Human Identification

This paper represents the first survey on the application of AI techniques for the analysis of biomedical images with forensic human identification purposes. Human identification is of great relevance in today’s society and, in particular, in medico-legal contexts. As consequence, all technological advances that are introduced in this field can contribute to the increasing necessity for accurate and robust tools that allow for establishing and verifying human identity. We first describe the importance and applicability of forensic anthropology in many identification scenarios. Later, we present the main trends related to the application of computer vision, machine learning and soft computing techniques to the estimation of the biological profile, the identification through comparative radiography and craniofacial superimposition, traumatism and pathology analysis, as well as facial reconstruction. The potentialities and limitations of the employed approaches are described, and we conclude with a discussion about methodological issues and future research.Spanish Ministry of Science, Innovation and UniversitiesEuropean Union (EU) PGC2018-101216-B-I00Regional Government of Andalusia under grant EXAISFI P18-FR-4262Instituto de Salud Carlos IIIEuropean Union (EU) DTS18/00136European Commission H2020-MSCA-IF-2016 through the Skeleton-ID Marie Curie Individual Fellowship 746592Spanish Ministry of Science, Innovation and Universities-CDTI, Neotec program 2019 EXP-00122609/SNEO-20191236European Union (EU)Xunta de Galicia ED431G 2019/01European Union (EU) RTI2018-095894-B-I0

Ancestral variation in mid-craniofacial morphology in a South African sample

Ancestry estimation is a critical component of the demographic profile compiled by forensic anthropologists when unknown skeletal remains are discovered. The mid-craniofacial region is most frequently used to estimate ancestry as this region reflects the genetic and morphological ancestry of an individual. The diverse composition of the South African population makes ancestry estimation problematic, and necessitates the development of reliable, population-specific standards. This study sought to characterise variations in mid-craniofacial shape and size between South Africans of European ancestry (EA), African ancestry (AA) and Mixed ancestry (MA). Metric, nonmetric and geometric morphometric assessments were performed on 392 crania from skeletal collections in South Africa. Variations in mid-craniofacial shape and size were assessed in the orbital, nasal, zygomatic and maxillary regions in two-and three-dimensions. Univariate and multivariate statistical analyses were employed to characterise variation and estimate ancestry in AA, MA and EA individuals. Multivariate analyses suggest that tightly integrated ancestral variations in each component of the mid-craniofacial region are associated with functional, regional and developmental proximities of these regions. Specifically, AA individuals exhibited wider and shorter midfacial regions than EA individuals, who exhibited the narrowest orbital, zygomatic and nasal breadths and the longest upper facial, orbital and nasal heights. EA individuals exhibited inferiorly-angled orbits, elongated nasal apertures and anteriorly projecting nasal bridges. Rounder nasal apertures, less anteriorly projecting nasal bridges and more anteriorly projecting maxillary regions were detected in AA individuals. MA individuals exhibited heterogeneity in terms of craniofacial shape and size, and therefore produced the lowest ancestry estimation accuracies. Overall, nasal and maxillary regions were the most ancestrally diverse regions. Antemortem maxillary tooth loss and midfacial trauma were confounding factors in ancestry estimation accuracies. The lowest ancestry estimation accuracies were yielded by two-dimensional metric (27%-60.2%) and nonmetric (57.1%-82.4%) methods. Metric and geometric morphometric assessments yielded the highest repeatability (≥ 95%) indicating that these methods may be more reliable for use in medicolegal contexts. Geometric morphometric shape assessments yielded the highest ancestry estimation accuracies (75-97.9%), suggesting the presence of three dimensional shape variations between ancestry groups. These results suggest that a continuum of ancestral variation, with large areas of overlap, exists across South African populations and emphasises the need to develop multivariate ancestry estimation standards which can estimate ancestry reliably

Evaluation of ancestry from human skeletal remains: a concise review

Ancestry assessment represents a major component of forensic anthropological analysis of recovered human remains. Interpretations of ancestry, together with other aspects of the biological profile, can help narrow the search of missing persons and contribute to eventual positive identification. Such information can prove useful to authorities involved in the identification and investigative process since many lists of missing persons have a reference to this parameter. Recent research has strengthened available methodologies involving metric, non-metric morphological as well as chemical and genetic approaches. This review addresses the new anthropological techniques that are now available, as well as the complex historical context related to ancestry evaluation.info:eu-repo/semantics/publishedVersio