Forensic identification by craniofacial superimposition using soft computing

Resumen

Forensic anthropology is the study of medico-legal questions relating to a deceased person through the examination of his or her skeletal remains, aiming among other things at determining the person's identity and the manner and cause of death. One of its most important applications is the identification of human beings from their skeletal remains, usually in the case of missing people, as well as under circumstances of war and mass disasters. This work involves comparing ante-mortem data (which can be retraced on the basis of visual material and interviews with relatives or witnesses) to the post-mortem data. This may involves a comparison of data pertaining to sex, age, stature, build and teeth. In order to put it into effect, the anthropologist measures and compares the skeleton data to determine the previous parameters. If this study shows positive results, more specific techniques are applied such as craniofacial superimposition, where photographs or video shots of the "disappeared person" are compared with the skull that is found. By projecting both photographs on top of each other (or, even better, matching a scanned three-dimensional skull model against the face photo/video shot), one can try to establish whether this is the same person. To do so, the matching of two sets of characteristic points (facial anthropometric landmarks in the subject photograph, and cranial anthropometric landmarks in the obtained photograph of the skull) is considered. It can be seen how the previous process has a clear relation with the image registration problem in computer vision from a computational point of view. The drawback of craniofacial superimposition identification is that there is no systematic method for the analysis by image superposition, but every researcher applies his own methodology. This is both due to the complexity of the projection procedure, and to the uncertainty inherent to the decision process since: a) the correspondence between facial and cranial anthropometric landmarks is not always symmetrical and perpendicular, and b) as final result, the identification decision can be expressed according to several confidence levels, depending on the chances of the sample (degree of conservation) and of the analytical process put into effect.