Katz v. United States
Citation: 389 U.S. 347 (1967)
Facts
Federal agents placed an electronic listening device on the outside of a public telephone booth used by Charles Katz to transmit illegal gambling information. The agents did not obtain a warrant. The government argued there was no Fourth Amendment violation because there was no physical trespass into the booth.
Issue
Whether the Fourth Amendment protects communications made in a public telephone booth from warrantless electronic surveillance, absent a physical intrusion.
Holding
The Supreme Court held that the warrantless wiretapping violated the Fourth Amendment. The Amendment protects people, not places, and a person who seeks to exclude the uninvited ear can rely on Fourth Amendment protection even in a public space.
Rule
The Fourth Amendment protects against government intrusions where a person has a reasonable expectation of privacy — a subjective expectation that society is prepared to recognize as objectively reasonable. Justice Harlan’s concurrence formulated this two-part test, which has become the controlling framework.
Significance
Katz superseded the property-based Olmstead doctrine and established the “reasonable expectation of privacy” test that governs modern Fourth Amendment analysis. It is the foundational case for all search and seizure law and is read alongside subsequent developments including Smith v. Maryland, Kyllo, and Carpenter v. United States.