For years, crime witnesses have been asked to come down to the police station and describe crime suspects to sketch artists. Recently, though, psychologists have found that when witnesses try to describe a face, they often distort their memory of it. Could there be a better way?
Police stations in the English county of Kent say they believe they have found one. This spring, they will introduce EigenFIT, one of several new programs that present a witness with a screen full of various photorealistic portraits. The witness chooses the portrait that seems to bear a resemblance, however slight, to the person he or she remembers. The computer then uses the chosen photo to produce a new generation of potential suspects, which the witness will again narrow down. Once more, the computer clones and mutates the chosen faces, slowly closing in on the face in question.
In order to create fresh sets of faces with enough variation, EigenFIT borrows tricks from evolution's playbook, causing traits to appear in a variety of combinations. After dozens of cycles, the computer-generated faces can no longer be distinguished from one another, and the police are left with a single lifelike portrait that no human sketch artist could possibly have drawn.
There is one potential problem: our memory of faces can be hazy and coarse, but the software creates images of fine-grained detail. In order to reduce the chances of a mistake, researchers have toyed with letting witnesses blur out the features they simply don't remember.