The present manual was designed to compile and illustrate the criteria to be used in the assessment of consistency between the superimposed skull and photography, analyzing anatomical criteria such as the concordance between the outlines of the face and the skull, the positional relationship of specific facial and skeletal features and soft tissue thickness.

The criteria included in this manual have been collected from the MEPROCS consortium (Damas y col., 2020), which established a protocol based on the previous works of Austin-Smith and Maples (1994), Yoshino et al. (1995; 2012), Chai et al. (2001), Jayaprakash et al. (2011), among others. The approach underlying this protocol requires a good knowledge of the anatomy of the skull and face.

This step of the CFS procedure is crucial to the whole process. An incorrect assessment of the anatomical relationship between the skeletal remains and the subject depicted in the AM image can result in incorrect conclusions. According to Yoshino et al. (1995; 2012), the authors stated that the skull can be positively identified as the presumed person if > 13 examination criteria are anatomically satisfied in the cranio-facial superimposition images. Thus, the authors recommend the adoption of both frontal and oblique or lateral face photographs for personal identification of the unknown skull by the superimposition method.

This manual offers a significant set of criteria extracted following on from a scientific study and international discussion (Ibáñez et al., 2016) on their discriminatory power and subjectivity. They can be seen as an effort in standardization of the criteria used by human-experts in evaluation of anatomical consistency in CFS. Considering that the available AM and PM data vary from case to case, the assessment criteria were divided into those that are usable in frontal and lateral/oblique views respectively. The different features and landmarks observed both on the skull and the superimposed image were classified into groups depending on their objectiveness and discriminatory power.

The expert should note that the condition described for a specific criterion is verified or not with a certain degree between strongly/moderately/limitedly consistent or not consistent. The verification of a criterion means the consistency between the skull and the face. The criteria that cannot be examined should be marked as undetermined.