Exploring the potential of cranial non-metric traits as a tool for personal identification: the never-ending dilemma

The potential of facial nevi in personal identification

Forensic anthropologists dealing with personal identification (PI) of human remains have recently stressed the need to explore the potential of "secondary identifiers" for identifying victims who died in particular events for whom images often represent the main antemortem data available. Being the face the part most exposed in images, characteristics as pigmented skin lesions (PSLs), can be crucial if combined with other input. Since no data is available on frequencies and distribution of facial PSLs in the general population, this study aims at systematically collecting such data to verify their potential in PI and to open a debate on the aid that "secondary identifiers", regardless of their specific nature, can give to the identification of the deceased in specific forensic contexts. A retrospective analysis on three-dimensional facial models of 1039 Italian subjects (from 4 to 84 years old) was conducted to examine the incidence of PSLs discriminated according to size and position in well-defined facial areas. From the collected data we developed a probabilistic approach providing the likelihood ratio (LR) for two settings: (1) the relative frequencies of nevi in the various facial areas, providing the deriving compound probability of owning a certain facial PSLs pattern; and (2) codes describing the facial nevi pattern of each individual of our population, thus testing their uniqueness and so their potential in PI. The calculated LRs mostly proved high identifying strength, particularly when provided by the compound probability-based approach. Data on incidence and position of facial nevi, their generated codes, and the probabilistic approach here presented, all constitute a starting point for advancing secondary identifiers. Nonetheless, although this preliminary study proved facial PSLs as valuable and potentially useful for identification, their significance and validity should be interpreted with caution as we are still at the first theoretical step clearly based on ideal conditions, and thus further investigations are due on the limitations of their use in practical identifying settings. Therefore, being this systematic study only a preliminary one in its nature, it is recommended not to use this kind of approach until further studies will test its validity in several practical conditions.

Rumor has it: A narrative review on the use of skeletal non-metric traits and variants for personal identification

The human skeleton displays an immense array of traits and variant features that are elements of inter-individual variability. The general assumption is that they may represent individualizing markers for the personal identification of unidentified decedents, but very few works consider them as such. This review provides an overview on the possible use of non-metric traits and skeletal variants for personal identification. The paper discusses the issues related to unquantified comparisons, then it presents a statistical approach based on frequencies of these features for identifying unknown remains. Narrowing down an initial number of 1000 papers, the core of the review is represented by 10 papers that considered non-metric traits and skeletal variants as individualizing features, according to both qualitative and quantitative assessments. Despite visual examination remains the gold-standard, more sound methods are requested to quantify the strength of a match or a mismatch. This especially applies in the wake of juridical demands, hence also satisfying the desire of prosecutors and judges to rely on a "quantified" risk. To this purpose, non-metric traits and skeletal variants seem to be a suitable tool to provide quantified evidence, when related frequencies are known.

Re-examining so-called 'secondary identifiers' in Disaster Victim Identification (DVI): Why and how are they used?

Disaster victim identification (DVI) refers to the identification of multiple deceased persons following an event that has a catastrophic effect on human lives and living conditions. Identification methods in DVI are typically described as either being primary, which include nuclear genetic markers (DNA), dental radiograph comparisons, and fingerprint comparisons, or secondary, which are all other identifiers and are ordinarily considered insufficient as a sole means of identification. The aim of this paper is to review the concept and definition of so-called 'secondary identifiers" and draw on personal experiences to provide practical recommendations for improved consideration and use. Initially, the concept of secondary identifiers is defined and examples of publications where such identifiers have been used in human rights violation cases and humanitarian emergencies are reviewed. While typically not investigated under a strict DVI framework, the review highlights the idea that non-primary identifiers have proven useful on their own for identifying individuals killed as a result of political, religious, and/or ethnic violence. The use of non-primary identifiers in DVI operations in the published literature is then reviewed. Because there is a plethora of different ways in which secondary identifiers are referenced it was not possible to identify useful search terms. Consequently, a broad literature search (rather than a systematic review) was undertaken. The reviews highlight the potential value of so-called secondary identifiers but more importantly show the need to scrutinise the implied inferior value of non-primary methods which is suggested by the terms "primary" and "secondary". The investigative and evaluative phases of the identification process are examined, and the concept of "uniqueness" is critiqued. The authors suggest that non-primary identifiers may play an important role in providing leads to formulating an identification hypothesis and, using the Bayesian approach of evidence interpretation, may assist in establishing the value of the evidence in guiding the identification effort. A summary of contributions non-primary identifiers may make to DVI efforts is provided. In conclusion, the authors argue that all lines of evidence should be considered because the value of an identifier will depend on the context and the victim population. A series of recommendations are provided for consideration for the use of non-primary identifiers in DVI scenarios.

Does sternal body shape reflect family relationships? A study on a genealogically documented Central European osteological sample (19th-20th centuries)

In forensic contexts, sternal anatomical varieties represent useful tools for the identification of an individual, either by comparison of ante-mortem and post-mortem data, or by potential comparison of data from biologically related individuals. Sternal body variation is also used to detect the biological affinity of individuals in bioarchaeology. However, no study has been made available to date on the degree to which the overall shape of the sternal body reflects the degree of biological relatedness. We, therefore, analyzed the sternal body shape of 10 individuals with known genealogical data, members of one family over three generations including inbred individuals (19th-20th centuries, Bohemia, Czech Republic), and a control sample of 12 biologically unrelated individuals. First, closely biologically related individuals were compared with unrelated individuals based on 10 variables expressing the morphological characteristics of the sternum, and then all individuals were compared based on Fourier analysis depending on their degree of relationship. The results showed that there is a greater degree of shape similarity in biologically related individuals than in unrelated individuals, and variability decreases with an increasing degree of relatedness. Inbred individuals showed the lowest sternum-shape distances and degree of variability, while unrelated individuals, showed the highest distances and variability. Moreover, in some cases, the documented relationships were also supported by a similar morphology of the ossified and fused xiphoid process. Thus, sternal shape analysis expands the possibilities for individual identification and the detection of the biological affinity of individuals for both the forensic sciences and bioarchaeology.

Nonmetric Variants of Anatolian Crania: A Preliminary Study

Analysis of nonmetric cranial variants has been essential for identifying the human population through osteologic analysis and genetic affinities. This study aimed to examine the nonmetric cranial variants to evaluate differences among sex and side correlations in Anatolian dry skulls. This study was carried out on 50 Anatolian adult dry human skulls (22 males, 28 females) with suitable features (nonfractured and/or with necessary features) out of a total of 97 dry skulls. After sex analysis, each skull was photographed from the norma frontalis, lateralis, inferior, and superior. Eleven nonmetrical cranial variants were investigated. The cranial variants and side incidences were analyzed to determine their sex differences and interside correlations. After the classification, traits were marked as "present" or "absent" on the charts. Some variants in female crania were seen more frequently than in males. Most of the variants such as the supraorbital notch, infraorbital and zygomaticofacial foramen, showed high correlations between the right and left sides. Overall, there were no statistically significant sex or side differences found in the Anatolian crania.