Katz v. United States

The Court held that the Fourth Amendment protects people and their reasonable expectations of privacy, not merely places.

Overview

FBI agents attached an electronic listening device to the outside of a telephone booth used by bookmaker Charles Katz. The Court overturned his conviction, abandoning the old property-based trespass doctrine. Justice Stewart wrote that the Fourth Amendment protects people, not places, and Justice Harlan's concurrence articulated the two-part test of a subjective expectation of privacy that society is prepared to recognize as reasonable. Katz governs modern surveillance law, from wiretaps to digital location data, and its reasonable expectation framework remains the threshold inquiry in every search and seizure case.