Answers: Forensic experts say that if features such as eye and hair color are determined by one or a few genes, identifying these traits of a suspect may be relatively simple, though height and weight may be harder, says Nigel Calder in "Magic Universe." A fascinating line of research regarding faces blends fundamental and forensic science. No two faces are ever exactly the same, not even those of identical twins. If Mother Nature varies human faces by shuffling a reasonably small number of genes, each definable face should be genetically traceable.

In fact, says Calder, researchers at University College of London have experimented with matching 3-D scans of volunteers' faces with their DNA samples. As medical physicist Alf Linney put it, "Sometime in the future we hope to be able to produce a photorealistic image of an offender's face, just from the DNA in a spot of blood or other body fluid found at a crime scene," i.e., leaving one's face in a DNA fingerprint.