## 2 Methodological Background
### Forensic Anthropology and Human Identification
For individuals who have not yet reached maturity (subadults), the methods proposed by [PERSON] and [PERSON] in 2004 [25] are recommended. 5. Age estimation of the living. The hand and wrist development atlas introduced in [26], the method for dental development proposed in [27], and the analysis of ossification status of the sternal epiphysis of the clavicle presented in [28] are recommended for different age ranges. Figure 2: Skeleton-based forensic identification (SFI) pipeline. These techniques can be applied for positive identification and potential candidates reduction (or shortlisting) of both living and dead individuals. They are commonly employed when other ID techniques (e.g., DNA or fingerprint comparison) are not applicable, or in combination with them. Age estimation of the living acquires special relevance when determining the legal age of the person being scrutinized (i.e., to determine if the person is 18 years old to carry out age-dependent legal procedures appropriately in accordance with the rule of law). * 6. Stature estimation is performed employing long bones. When the remains are contemporary and of Mediterranean origin, it is recommended to use the formulas proposed in [29] for the femur and humerus, and those proposed in [30] for the tibia. When the remains are from the North American population, the formulas proposed in [31] as well as the FORDISC computer program [32] will preferably be applied. * 7. The estimation of population ancestry is the most inaccurate element of the BP given the low reliability of its results. It should only be used as an orientation criterion when there is a good agreement between the human study groups and skeletal biology, giving preference to morphological criteria of the skull. * **Comparative radiography (CR)** involves the direct comparison of AM radiographs, generally acquired for medical reasons, with PM radiographs acquired only for ID purposes, using specific and individualizing structures. Both radiographs are visually compared and evaluated for similarity in osseous shapes and densities, to determine whether they belong to the same subject [33]. Several bones and cavities have been reported as useful for candidate short-listing or positive identification based on their individuality and uniqueness. In particular, the most widely recognized as useful and reliable methods of identification are teeth, frontal cranium bones, vertebas, and clavicles, although dental-based ID is the most employed and discriminative technique. Also, the most commonly AM and PM images employed with the CR technique include radiographs [34], CT images [35], and 3D surface models [36]. The application of CR requires the superimposition of the AM and PM data for their visual comparison by producing PM radiographs simulating the AM ones in scope and projection. This is a time-consuming and error-prone trial-and-error process that relies completely on the skills and experience of the analyst. CR requires a prior record of clinical images not always available, but if present, this technique can be extremely accurate, reaching 100% reliability for certain bones [37]. The whole CR-based ID process is depicted in Figure 3.  
**Craniofacial Superimposition (CFS)** is probably the most challenging SFI method [38; 39]. It involves the superimposition of an image of a skull with a number of AM face images of an individual and the analysis of their morphological correspondence. This skull-face overlay (SFO) process  
Figure 3: General comparative radiography (CR)-based ID process. After data acquisition and processing (e.g., anatomical regions of interest segmentation), and prior to decision making, the ante-mortem (AM) and post-mortem (PM) materials are registered, so their overlap is maximized. In this figure, this superimposition process is depicted using frontal sinuses in X-Ray images. is usually done by corresponding anatomical (anthropometrical) landmarks located in the skull (craniometric) and the face (cephalometric).