Nothing in American police work is more controversial than racial profiling. Minorities are targeted for small offenses in the hope of uncovering bigger crimes, and the practice has generated successful lawsuits by the ACLU and pledges from state governments and law enforcement agencies to clean up their discriminatory acts. Add to this charged atmosphere the prospect of a DNA-race angle. By now most Americans know that when criminals leave traces of themselves―blood, semen, hair, a scrape of skin under a victim's fingernails―at crime scenes, they leave a unique genetic fingerprint that can establish their presence at the scene with great certainty. Less known but more controversial is that DNA traces also leave clues about ancestry and appearance, clues that, as genetic science matures, might be used to generate a sort of police sketch.
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