Construction of Facial Composites from Eyewitness Memory

Law enforcement agencies often rely on practical technologies to help witnesses and victims of crimes construct likenesses of faces from memory. These face composites are typically circulated to law enforcement officers and made accessible to the public in the hope that someone familiar with the depicted person will recognise their likeness and thus provide the police with a suspect. We will review methods for constructing such likenesses from memory dating back to the portrait parle of Alphonse Bertillon (Signaletic instructions including the theory and practice of anthropometrical identification. Werner Company, 1896) and the composite images of Francis Galton (Nature 18:97-100, 1878). We will also review more modern methods, ranging from the overlay techniques of Identi-Kit (McDonald, c 1959) and Photo-Fit (Penry J. The Police Journal 43:307, 1970) to feature-based computerised composite systems such as Identi-Kit 2000, FACES, and ProMat. Most early systems were based on the common-sense notion that sectioning a face is invertible: just as a face can be sectioned into components, so it can be recreated by arrangements of sections. This assumption appears to be unwarranted. The underlying problem with earlier face systems may have been the absence of a representational or computational theory. This led in the late 1990s to the development of the so-called third-generation holistic composite systems, which are based on underlying statistical and mathematical models of face images (e.g. ID [Tredoux et al. South African Computer Journal 2006:90-97, 2006], EvoFIT [Frowd CD, Hancock PJB, & Carson D. ACM Transactions on Applied Psychology (TAP) 1:1-21, 2004a], E-FIT [Gibson et al., International Conference on Visualisation, 146-151, 2003]). A special focus of the chapter will be on these newer technologies and other recent technological innovations. Our approach will be to review (i) the methods of operation, (ii) the techniques identified by psychologists and other researchers for improving the quality of information obtained from memory, and (iii) the empirical data on the effectiveness of these systems at representing faces from memory. We will consider related issues, too, including the question of whether face composites damage witness memory, and the ethics of face composition.