Three minutes after California's new automated fingerprint identification system received its first assignment, the crime-stopping computer scored a direct hit. It matched a smudged print lifted from an orange Toyota in Los Angeles to one taken from a 25-year-old drifter with a record of drug and auto-theft arrests. Two days later, Richard Ramirez was caught and charged with one of 15 murders attributed to the Night Stalker, the serial killer who had been terrorizing the city for the past seven months.
The speedy identification of Ramirez was the latest and most dramatic example of a technique that has police officials across...