Katz v. United States
Does the Fourth Amendment's protection against unreasonable searches and seizures apply to electronic surveillance of a person's conversation in a public telephone booth, even when there is no physical intrusion into the booth itself?
The Decision
7-1 decision · Opinion by Potter Stewart · 1967
Majority Opinion— Potter Stewartconcurring ↓dissent ↓
In a 7–1 decision authored by Justice Potter Stewart, the Supreme Court reversed Katz's conviction and held that the Fourth Amendment protects people, not places, and that its reach cannot depend on the presence or absence of a physical intrusion into a given enclosure. The Court declared that what a person 'seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.' When Katz stepped into the phone booth and shut the door behind him, he was entitled to assume that his words would not be broadcast to the world — and the Fourth Amendment protected that justified expectation.
The majority explicitly rejected the old framework that had governed Fourth Amendment analysis for nearly four decades, which asked whether the government had committed a physical trespass into a 'constitutionally protected area.' Justice Stewart wrote that the 'correct solution of Fourth Amendment problems is not necessarily promoted by incantation of the phrase constitutionally protected area.' The Fourth Amendment protects people, and it follows a person wherever they go — even into a glass-walled telephone booth on a public street. What matters is not the physical characteristics of the location, but whether the individual's expectation of privacy is one that society would consider reasonable.
The Court acknowledged that the FBI agents acted with some restraint. They knew which booth Katz used, they limited their surveillance to short periods, and they only listened when Katz was present. But the Court held that this restraint, however commendable, was no substitute for the constitutional requirement of prior judicial authorization. The agents never obtained a warrant or sought any kind of judicial approval before conducting their surveillance. Under the Fourth Amendment, 'searches conducted outside the judicial process, without prior approval by judge or magistrate, are per se unreasonable,' subject only to a few well-defined exceptions — none of which applied here.
The Court therefore concluded that the government's warrantless electronic eavesdropping on Katz's telephone conversations violated the Fourth Amendment. The recordings should have been suppressed, and Katz's conviction was reversed. Justice Thurgood Marshall took no part in the consideration or decision of the case.
Concurring Opinions
Justice John Marshall Harlan II wrote an influential concurrence that articulated what became the dominant framework for Fourth Amendment analysis: a two-part test asking first whether a person exhibited an actual, subjective expectation of privacy, and second whether that expectation is one that society is prepared to recognize as objectively reasonable. Justice William O. Douglas, joined by Justice William J. Brennan Jr., wrote a concurrence emphasizing that the executive branch should not be allowed to determine on its own when surveillance is permissible, and that only a magistrate can authorize a search. Justice Byron White also wrote a concurrence addressing the scope of warrant exceptions.
Dissenting Opinions
Hugo Black
Justice Black argued that the Fourth Amendment was written to protect against the search and seizure of tangible things — persons, houses, papers, and effects — and was never intended to protect the privacy of conversations. He believed the majority was effectively rewriting the Constitution by reading a general right of privacy into an amendment that contains no such language, a task that should be left to the people through the amendment process, not to judges.
- The text of the Fourth Amendment specifically lists 'persons, houses, papers, and effects' — all tangible, physical things — and eavesdropping on conversations does not involve the search or seizure of any of these items
- By transforming the Fourth Amendment into a broad guarantee of privacy, the Court was engaging in judicial legislation and departing from the original meaning of the Constitution as understood by its framers
- The word 'privacy' appears nowhere in the Fourth Amendment, and if the American people want to outlaw wiretapping and eavesdropping, they should pass laws or adopt a constitutional amendment rather than relying on judges to stretch existing language beyond its meaning
- The majority's approach gives judges nearly unlimited discretion to decide what expectations of privacy are 'reasonable,' which provides no clear standard and invites unpredictable, subjective decision-making
Background & Facts
Charles Katz was a professional gambler based in Los Angeles. In February 1965, FBI agents suspected him of illegally transmitting wagering information by telephone to contacts in Miami and Boston, a violation of a federal wire statute. Agents identified a cluster of three public telephone booths on Sunset Boulevard that Katz regularly used at predictable times. Rather than entering the booth or tapping the phone line in a traditional sense, the agents attached a small electronic listening and recording device to the outside of the phone booth. Over the course of six days, they recorded Katz's side of his telephone conversations, capturing him placing bets and relaying gambling information across state lines.
Katz was charged with transmitting wagering information by telephone in interstate commerce, in violation of federal law. At trial, the government introduced the FBI's recordings of his phone booth conversations as evidence. Katz moved to suppress the recordings, arguing that the surveillance violated his Fourth Amendment right to be free from unreasonable searches and seizures. The trial court admitted the recordings, and Katz was convicted on eight counts.
Katz appealed to the United States Court of Appeals for the Ninth Circuit, which affirmed his conviction. The Ninth Circuit relied on existing Supreme Court precedent holding that the Fourth Amendment only protected against physical trespass into a constitutionally protected area. Because the FBI's listening device was placed on the outside of the phone booth and never physically penetrated the booth's walls, the court concluded there was no 'search' under the Fourth Amendment. The eavesdropping was therefore considered lawful even without a warrant.
The Supreme Court agreed to hear the case because it raised a fundamental question about the scope of Fourth Amendment protections in an era of rapidly advancing surveillance technology. The prevailing legal framework, rooted in decades-old precedent, held that Fourth Amendment rights were tied to physical spaces and tangible property. Katz's case presented an opportunity to reconsider whether that framework adequately protected individual privacy in a modern world where the government could intrude on private conversations without ever physically trespassing on anyone's property or possessions.
The Arguments
Katz argued that the Fourth Amendment protects people, not just physical places, and that he had a right to make a private phone call from a telephone booth without government eavesdropping. He maintained that the FBI's warrantless electronic surveillance of his conversations constituted an unreasonable search, regardless of whether agents physically entered the booth.
- When Katz entered the phone booth and closed the door, he had every right to expect that his conversation was private and not being intercepted by the government
- The Fourth Amendment should not be limited to cases of physical trespass — what matters is the invasion of privacy, not whether agents broke into a physical space
- The FBI could easily have obtained a judicial warrant authorizing the surveillance, and by failing to do so, they conducted an unreasonable search in violation of the Constitution
The government argued that the Fourth Amendment only protects against physical intrusions into constitutionally protected areas such as homes or offices. Because the FBI's listening device was placed on the outside of the phone booth and never physically penetrated the booth, there was no 'search' requiring a warrant.
- Under long-standing Supreme Court precedent, a search only occurs when the government physically trespasses into a protected area, which did not happen here
- A public telephone booth is not a constitutionally protected area like a home — it is a partly transparent structure visible to passersby, and Katz voluntarily used a public facility
- Even if the surveillance were deemed a search, the agents acted with great restraint, limiting their monitoring to brief periods when Katz was actually using the phone, which should satisfy any reasonableness requirement