I assume that you are asking about the case of Katz v. United States, which was decided in 1967. This was a case that centered around the issue of whether the government is allowed to place a wiretap on a public telephone without getting a warrant to do so. The facts have to do with a person using a public telephone to conduct gambling operations across state lines.
Charles Katz was a bookie in Los Angeles. He would place bets with other illegal gambling operations in places like Miami and Boston. He believed that his own telephone was bugged and so he typically went out of his apartment to use a pay phone. Pay phones in those days often were in booths with glass walls and folding doors. Katz felt he could not be heard in the booth.
The FBI observed Katz using the phone booths regularly. They believed he was using them to transmit gambling information across state lines. Therefore, they placed taps on the booth that could pick up Katz’s end of the conversations. Katz was overheard transmitting gambling information. The recordings made of Katz were used to prosecute him. He appealed, arguing that the taps were illegal searches.