Poor reliability of facial indices for comparative metric facial identification without parametrical superimposition.

The relationship between the craniometric indices that can be evinced from the comparison of two faces for identification purposes is considered a reliable method for the personal identification of faces. Our study aims to assess whether facial indices are susceptible to substantial variations even if the two faces being compared are a different size, looking in a different direction, or differently angled. Our results showed high variability as regards both the facial indices thus obtained and the relative relations. This underlines the fact that regardless of the validity of the metric analysis method used, no numerical comparison can be reliable unless prior parametrical somato-physical superimposition of the images of the subjects has been performed to assess the complete comparability of the faces of the suspects. In conclusion, no reliable identification can be made with the simplified techniques that bypass this difficult, demanding and time-consuming phase of parametric superimposition, as we have shown that they can lead to gross errors.