Search and Seizure | Facts: In a U.S. district court, Charles Katz was convicted of transmitting wagering information by telephone. At his trial, the prosecution was permitted to introduce evidence of Katz's portion of telephone conversations, despite defense counsel's objection. Federal Bureau of Investigation agents had attached an electronic eavesdropping and recording device to the outside of the public telephone booth Katz used. | Issue: Was the evidence obtained through a legal surveillance (electronic eavesdropping)? | Decision: Admitting such evidence was a reversible error, in view of the lack of prior judicial authorization (search warrant)