"Give me Duquesne minus 7, for a nickel."

It was February 1965 on a lonely section of Los Angeles's Sunset Boulevard, and Charles Katz, one of life's little losers, was placing an illegal sports bet over a public telephone. Unbeknownst to Katz, however, the FBI had placed a microphone atop the telephone booth to record this small-time gambler's conversations.

Engineers often mock the law for lagging behind technology. In fact, the law is often far ahead of it. This time it was ahead by nearly 200 years, for after Katz's arrest his lawyers argued that although the framers of the Constitution could not possibly have encountered tape recorders and telephone booths, the Fourth Amendment's ban on "unreasonable" searches nonetheless covered them. Because the FBI had no search warrant, Katz's lawyers said, bugging the phone booth was illegal. In a landmark decision, the Supreme Court agreed, affirming for the first time that electronic surveillance was-constitutionally speaking-a search. "No less than an individual in a business office, in a friend's apartment, or in a taxicab," the majority declared, "a person in a telephone booth may rely upon the protection of the Fourth Amendment."