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Perhaps the most futuristic of the new crime-busting technologies, and one that is also the subject of disputes, is a procedure known as brain fingerprinting (see box). The principle behind the technique is that when the brain processes an image it recognizes (as opposed to one it has never seen before), it emits distinct electrical impulses that are detectable by scalp sensors. A positive response to a photo of a crime scene may mean a suspect was there before; a negative response may help confirm an alibi.
Other technologies are less experimental. One of the fondest dreams of law-enforcement officials is to build a national computer system that holds the fingerprints and DNA of every known felon and the ballistic signature of every gun ever used in a crime. Early versions of each of these databases--the Combined DNA Index System (CODIS), the National Integrated Ballistics Information Network (NIBIN) and the Integrated Automated Fingerprint Identification System (IAFIS)--already exist, but they are not yet all fully operational.
The ballistics network has been slow getting implemented nationwide. But when it works, it works well. Kareem Willis, 20, was arrested last year in New York City for armed robbery. When police tested his gun, they were able to link it to four shootings and three deaths. He's now serving 25 years to life for two of those killings. "We have evidence sitting in here linked to numerous other crimes," says Detective Mike Boncimino. "Eventually they're going to get caught with the gun."
The DNA database is also nowhere near complete, in part because of the legal complexities of obtaining DNA samples. In California a program that required felons to submit DNA samples was challenged by a group of female inmates on death row who claimed it would violate their privacy. They and several hundred other inmates refused to give up their DNA. The state supreme court slapped down the suit by refusing to review the matter, and last month Governor Gray Davis signed legislation allowing jail officials to take samples by force if necessary. "I logically cannot see the difference between a person's fingerprint and a DNA fingerprint," says Lisa Kahn, a Los Angeles prosecutor. Argues Peter Neufeld, co-founder of the Innocence Project: "Fingerprints don't tell you anything other than a fingerprint." With DNA, "there is potentially a lot more information about people that we may not want to share with the government. How would you feel about it if your complete DNA profile was kept in Washington with the Department of Health?"
The irony is that DNA evidence can also clear a condemned prisoner. Earlier this month Montana inmate Jimmy Ray Bromgard, who had already spent 15 years in jail, became the 111th person in the U.S. exonerated by postconviction DNA testing aided by the Innocence Project after it was revealed that semen found on the victim's clothing was not, in fact, his.