King County, Wash., detective Robert Keppel was hunting a serial murderer in 1974. Working from the leanest of clues, his staff assembled some 30 lists of potential suspects. One named 4,000 University of Washington classmates of a female victim. Another, every patient released from the state's mental wards in the preceding decade. Using a punch-card computer, the investigators compared the lists. Among the 25 that turned up most often was one now-infamous name: Ted Bundy.

Keppel, currently chief criminal investigator with the Washington State attorney general's office, says that rudimentary program was the first ever written to catch a killer. Today, Keppel is again helping to pioneer crime-fighting computing by testing a new system developed at the Pacific Northwest National Laboratory in Richland, Wash. Called Computer Aided Tracking and Characterization of Homicides (CATCH), it uses a neural network to discover unseen patterns in the state's computerized murder-investigation records.