Police suspected that Charles Katz was using a public phone booth to discuss gambling wagers across state lines. The FBI attached an electronic listening device on the outside of the booth after gathering a substantial amount of evidence against Katz. The recordings from the eavesdropping device were used to convict Katz in his trial. Katz appealed, claiming that using the eavesdropping device violated the Fourth Amendment. The Court of Appeals ruled in favor of the FBI, as the device was placed on the outside of the public phone booth, where anyone standing nearby could have heard the conversation. If the device had been place in the phone booth, the Court of Appeals would have ruled that the device unreasonably intruded on Katz, which violates the Fourth Amendment. The Supreme Court rejected the Court of Appeals’ decision and ruled on Katz’s behalf. Justice Stewart wrote the majority opinion, saying that an individual’s conversations are constitutionally protected if they are made with the reasonable expectation of privacy. Katz entered the phone booth and shut the door behind him expecting that the audience would remain limited to the person on the other end of the line. Katz had argued that the recordings violated the Fourth Amendment’s protection against unreasonable intrusion. The court, however, looked to a different clause in the amendment because the protection against unreasonable intrusion applies to people, not locations. Justice Stewart classified wiretapping as a “search”, thus requiring a warrant. The court ruled that the eavesdropping device’s recordings were illegally obtained, as no search warrant was secured.

Katz v. United States

389 U.S. 347 (1967)

(The REP Case)


The petitioner was convicted in the District Court for the Southern District of California under an eight-count indictment charging him with transmitting wagering information by telephone from Los Angeles to Miami and Boston, in violation of a federal statute. At trial the Government was permitted, over the petitioner's objection, to introduce evidence of the petitioner's end of telephone conversations, overheard by FBI agents who had attached an electronic listening and recording device to the outside of the public telephone booth from which he had placed his calls.       

Katz v. United States 389 U.S. 347 (1967)

Katz v. United States 389 U.S. 347 (1967)


Whether the search and seizure conducted in this case complied with constitutional standards.    


The Fourth Amendment protects people, not places. What a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection.

The Government stresses the fact that the telephone booth from which the petitioner made his calls was constructed partly of glass, so that he was as visible after he entered it as he would have been if he had remained outside. But what he sought to exclude when he entered the booth was not the intruding eye -- it was the uninvited ear. He did not shed his right to do so simply because he made his calls from a place where he might be seen. One who occupies it, shuts the door behind him, and pays the toll that permits him to place a call is surely entitled to assume that the words he utters into the mouthpiece will not be broadcast to the world. To read the Constitution more narrowly is to ignore the vital role that the public telephone has come to play in private communication.

The Fourth Amendment governs not only the seizure of tangible items, but extends as well to the recording of oral statements, overheard without any "technical trespass under . . . local property law." Once this much is acknowledged, and once it is recognized that the Fourth Amendment protects people -- and not simply "areas" -- against unreasonable searches and seizures, it becomes clear that the reach of that Amendment cannot turn upon the presence or absence of a physical intrusion into any given enclosure.

Accepting this account of the Government's actions as accurate, it is clear that this surveillance was so narrowly circumscribed that a duly authorized magistrate, properly notified of the need for such investigation, specifically informed of the basis on which it was to proceed, and clearly apprised of the precise intrusion it would entail, could constitutionally have authorized, with appropriate safeguards, the very limited search and seizure that the Government asserts in fact took place.

It is apparent that the agents in this case acted with restraint. Yet the inescapable fact is that this restraint was imposed by the agents themselves, not by a judicial officer. They were not required, before commencing the search, to present their estimate of probable cause for detached scrutiny by a neutral magistrate. They were not compelled, during the conduct of the search itself, to observe precise limits established in advance by a specific court order. Nor were they directed, after the search had been completed, to notify the authorizing magistrate in detail of all that had been seized. In the absence of such safeguards, this Court has never sustained a search upon the sole ground that officers reasonably expected to find evidence of a particular crime and voluntarily confined their activities to the least intrusive means consistent with that end. Searches conducted without warrants have been held unlawful "notwithstanding facts unquestionably showing probable cause," for the Constitution requires "that the deliberate, impartial judgment of a judicial officer . . . be interposed between the citizen and the police . . .." The mandate of the [Fourth] Amendment requires adherence to judicial processes,"and that searches conducted outside the judicial process, without prior approval by judge or magistrate, are per se unreasonable under the Fourth Amendment -- subject only to a few specifically established and well-delineated exceptions.

It is difficult to imagine how any of those exceptions could ever apply to the sort of search and seizure involved in this case. Even electronic surveillance substantially contemporaneous with an individual's arrest could hardly be deemed an "incident" of that arrest. Nor could the use of electronic surveillance without prior authorization be justified on grounds of "hot pursuit." And, of course, the very nature of electronic surveillance precludes its use pursuant to the suspect's consent.

Wherever a man may be, he is entitled to know that he will remain free from unreasonable searches and seizures. The government agents here ignored "the procedure of antecedent justification . . . that is central to the Fourth Amendment," a procedure that we hold to be a constitutional precondition of the kind of electronic surveillance involved in this case. "   

Justice Stewart decides Katz v. United States


The Government's activities in electronically listening to and recording the petitioner's words violated the privacy upon which he justifiably relied while using the telephone booth and thus constituted a "search and seizure" within the meaning of the Fourth Amendment. The fact that the electronic device employed to achieve that end did not happen to penetrate the wall of the booth can have no constitutional significance.

Key Concurrence:

Harlan Concurrence: My understanding of the rule that has emerged from prior decisions is that there is a twofold requirement, first that a person have exhibited an actual (subjective) expectation of privacy and, second, that the expectation be one that society is prepared to recognize as "reasonable."

Is there anything we missed? Anything we should remove? Let us know your thoughts!

Key Takeaway

In Katz, the Supreme Court concurrence established that a search occurs if and only if a reasonable expectation of privacy (REP) is violated. REP requires that 1) Defendant expected privacy and it's exhibited, and 2) Society is prepared to recognize the expectation of privacy as reasonable.

Court Syllabus:

Petitioner was convicted under an indictment charging him with transmitting wagering information by telephone across state lines in violation of 18 U. S. C. § 1084. Evidence of petitioner's end of the conversations, overheard by FBI agents who had attached an electronic listening and recording device to the outside of the telephone booth from which the calls were made, was introduced at the trial. The Court of Appeals affirmed the conviction, finding that there was no Fourth Amendment violation since there was "no physical entrance into the area occupied by" petitioner. 


1. The Government's eavesdropping activities violated the privacy upon which petitioner justifiably relied while using the telephone booth and thus constituted a "search and seizure" within the meaning of the Fourth Amendment.

(a) The Fourth Amendment governs not only the seizure of tangible items but extends as well to the recording of oral statements.

(b) Because the Fourth Amendment protects people rather than places, its reach cannot turn on the presence or absence of a physical intrusion into any given enclosure. The "trespass" doctrine of Olmstead v. United States and Goldman v. United States is no longer controlling.

2. Although the surveillance in this case may have been so narrowly circumscribed that it could constitutionally have been authorized in advance, it was not in fact conducted pursuant to the warrant procedure which is a constitutional precondition of such electronic surveillance. 

How the Justices Voted

Majority: Stewart, joined by Warren, Douglas, Harlan, Brennan, White, Fortas

Concurrence: Douglas, joined by Brennan

Concurrence: Harlan

Concurrence: White

Dissent: Black