When you see a police sketch of a criminal suspect in the news, it means the detectives have next to no information about the person they're looking for. All they have is a memory locked inside the brain of the victim or a witness.
For decades, police sketch artists have tried to translate those memories into pictures by interviewing victims and drawing until the victims are satisfied with the likeness. In some cases, the sketches turn out to be quite accurate. This sketch of Oklahoma City bomber Timothy McVeigh was based on a description by employees of the place where he rented the van:
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The sketch reportedly convinced police not to release McVeigh, whom they had arrested for driving without plates and carrying a weapon without a permit.
But more frequently, the sketch doesn't end up resembling the perpetrator at all. And that's because we're generally terrible at describing faces from memory.
Check out the video above to learn about the psychological processes that limit our ability to communicate memories of faces, and see how new computer programs for facial composites could be the future of the police sketch.
