Image Comparison: Facial, Photographic

Abstract

Photographic facial image comparison analysis refers to techniques designed to determine whether two or more photographic images depict the same person or not. One of the images will normally either be the suspect in a police investigation, or the defendant in court. Comparison crime scene evidence will often be images acquired from sources such as closed circuit television cameras (CCTV). There are three primary techniques used by expert witnesses to present opinion evidence of identity in court. With photoanthropometric analysis, the proportional distances and angles between specified facial features visible in photographs are measured and compared across evidence. With morphological comparison analysis, facial features are visually inspected and classified into predetermined categories. Finally, with photographic superimposition analysis, one photograph or video still is superimposed over a second, to perform a series of visual inspections. The forensic reliability of each method with two‐dimensional photographs is questionable, particularly, if the image quality is poor, or the facial viewpoints in different images do not match. Furthermore, expert opinion of identity evidence is rarely accompanied with statistical margins of error, or the probability that images depict two different individuals. Nevertheless, recent innovations using three‐dimensional image capture technology have suggested that in the future, there may be improvements in the reliability of photographic facial image comparison techniques.