The FBI suspected Charles Katz of transmitting wagering information by telephone in violation of federal gambling laws. Katz regularly used a series of public telephone booths in Los Angeles to place calls to contacts in Boston and Miami. Without obtaining a warrant, FBI agents attached an electronic listening and recording device to the outside of the phone booth Katz used. The device captured Katz's end of the conversations but did not physically penetrate the booth. At trial, the government introduced the recordings to prove Katz's involvement in illegal gambling, and he was convicted. The Ninth Circuit affirmed, reasoning that there was no Fourth Amendment violation because there was no physical intrusion into the booth. The U.S. Supreme Court granted certiorari.
Does the warrantless electronic recording of a person's conversation from outside a public telephone booth, where the speaker has sought to preserve privacy, constitute a search and seizure in violation of the Fourth Amendment?
The Fourth Amendment protects people, not places. A search occurs when the government violates a person's subjective expectation of privacy that society recognizes as reasonable. Physical trespass is not required. Absent a specifically applicable exception, electronic surveillance of private conversations requires a warrant supported by probable cause and particularity.
Yes. The government's warrantless electronic eavesdropping on Katz's conversation in a closed public phone booth violated the Fourth Amendment. The conviction was reversed.
The Court, per Justice Stewart, emphasized that the Fourth Amendment protects the privacy of people rather than the sanctity of physical locations. Katz's conduct—entering a phone booth, closing the door, and paying to make a call—manifested a subjective expectation of privacy in the content of his conversation. Society is prepared to recognize that expectation as reasonable, even though the booth is in a public place. The Court rejected the notion that a search requires physical penetration of a protected area, disavowing the property-centric approach associated with cases like Olmstead v. United States and Goldman v. United States. The government's attachment of a listening device to the exterior of the booth and its recording of Katz's words intruded upon the privacy of his communication and thus constituted a "search and seizure" within the meaning of the Fourth Amendment. The Court also explained that when the government seeks to intrude upon such privacy, it must obtain a warrant, unless a recognized exception applies. No exigent circumstances or other exceptions justified the FBI's surveillance here, and the agents could have pursued a warrant tailored to the particular conversations and times at issue. Justice Harlan's concurrence articulated the now-canonical two-prong test: (1) the individual exhibited an actual (subjective) expectation of privacy, and (2) that expectation is one society is prepared to recognize as reasonable. Applying that framework, Katz's expectation was both demonstrated and reasonable. Justice White concurred to underscore that national security wiretaps might present different questions. Justice Black dissented, arguing that the text of the Fourth Amendment does not cover eavesdropping on words absent a physical search of "persons, houses, papers, and effects."
Katz is the cornerstone of modern Fourth Amendment law. It recast the definition of a search in terms of reasonable expectations of privacy, enabling the Constitution to regulate emerging forms of surveillance without requiring a physical trespass. The decision directly informs analysis of electronic eavesdropping and has been extended to technologies like thermal imaging (Kyllo v. United States) and cell-site location data (Carpenter v. United States). At the same time, Katz coexists with doctrines limiting privacy expectations, such as the third-party doctrine (Smith v. Maryland; United States v. Miller), and with renewed attention to trespass as an additional, not exclusive, basis for finding a search (United States v. Jones). For law students, Katz provides the analytic template for Fourth Amendment questions: identify the individual's asserted privacy interest, assess whether the person exhibited a subjective expectation, evaluate whether that expectation is objectively reasonable, and determine whether a warrant or exception applies. It also influenced legislative responses, notably Title III of the Omnibus Crime Control and Safe Streets Act of 1968, which set procedures for wiretaps consistent with Katz's requirements.
Katz v. United States reoriented Fourth Amendment analysis around privacy rather than property. By recognizing that a person who enters a phone booth, closes the door, and pays to make a call seeks to preserve the privacy of their conversation, the Court announced that the Constitution protects reasonable expectations of privacy, even in spaces accessible to the public.