This is an audio case brief of Katz v. United States, 389 U.S. 347 (1967). The audio brief provides a full case analysis. However a written summary of the case is provided below.

Table of Contents


Charles Katz was charged under an eight count indictment for transmitting wagering information by telephone from Los Angeles to Miami and Boston in violation of a federal statute. Katz was overheard by FBI agents who attached an electronic listening and recording device to the outside of the public telephone booth from which he placed his calls.

He was convicted of these charges. During his trial, the Government was permitted, over Katz’s objection, to introduce evidence of Katz’s end of the telephone conversation.

Katz appealed his conviction to the court of appeals. The court affirmed his conviction. The court of appeals rejected Katz contention that the recordings had been obtained in violation of the Fourth Amendment. The court reasoned that because ‘(t)here was no physical entrance into the area occupied by Katz, his fourth amendment rights were not violated.

The U.S Supreme court granted certiorari to review his case.


  • Whether Katz’s had a reasonable expectation of privacy for his conversation in a visible telephone booth, which was obtained by the government through an electronic device, without physical trespass.

** Note: This first issue is to determine whether the officer’s conducted was a search which would require a warrant.

  • Whether the officer’s conduct, which was done without a warrant could be retroactively validated by the court.


What a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection. But what he seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected.


The government argued that because the telephone booth from which  Katz 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, he had no reasonable expectation of privacy.

But the court disagreed.

The court reasoned that what Katz sought to exclude when he entered the booth was not the intruding eye—it was the uninvited ear. And 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 a telephone booth, 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 government further argued that the activities of its agents in this case should not be tested by Fourth Amendment requirements because the surveillance technique they employed involved no physical penetration of the telephone booth from which the Katz  placed his calls.

But Again the court disagreed with the government.

The court stated that it is true that the absence of such penetration was at one time thought to foreclose further Fourth Amendment inquiry. Although a closely divided Court supposed in Olmstead that surveillance without any trespass and without the seizure of any material object fell outside the ambit of the Constitution, we have since departed from the narrow view on which that decision rested. Indeed, we have expressly held that 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.


In conclusion for the first issue, the court ruled that the Government’s activities in electronically listening to and recording Katz’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.


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.


The government argued that that its agents acted in an entirely defensible manner: They did not begin their electronic surveillance until investigation of Katz’s activities had established a strong probability that he was using the telephone in question to transmit gambling information to persons in other States, in violation of federal law. Moreover, the surveillance was limited, both in scope and in duration, to the specific purpose of establishing the contents of Katz’s unlawful telephonic communications. The agents confined their surveillance to the brief periods during which he used the telephone booth, and they took great care to overhear only the conversations of the petitioner himself.

The government further argued that because its agents relied upon the decisions in Olmstead and Goldman where eavesdropping without a physical trespass was not a search within the meaning of the fourth amendment, and because they did no more here than they might properly have done with prior judicial sanction, the Court should retroactively validate their conduct.

But the court once again, disagreed with the government.

The court reasoned that even if the governments assertions  are taken as true, the inescapable fact is that the restraint the agents exercised in conducting the search 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. Over and again this Court has emphasized that 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.

The court found that none the narrow exceptions applied in this case. The search was not conducted incident to an arrest, it was not conducted under hot pursuit, nor was it conducted with Katz consent.


Katz had a reasonable expectation of privacy in the phone booth. The agents listening to his side of the conversation was a search that required a warrant. And because the agents did not obtain a warrant to conduct that search, his conviction was reversed by the court.

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