Katz v. United States: Supreme Court Case, Arguments, Impact

Redefining Search and Seizure in the Fourth Amendment

Traditional American phone booth

Annabelle Breakey / Getty Images

Katz v. United States (1967) asked the Supreme Court to decide whether wiretapping a public phone booth requires a search warrant. The Court found that an average person has an expectation of privacy while making a call in a public phone booth. As a result, agents violated the Fourth Amendment when they used electronic surveillance to listen in on a suspect without a warrant.

Fast Facts: Katz v. United States

  • Case Argued: October 17, 1967
  • Decision Issued: December 18, 1967
  • Petitioner: Charles Katz, a handicapper who specialized in wagering in college basketball
  • Respondent: United States
  • Key Questions: Can police officers wiretap a public payphone without a warrant?
  • Majority: Justices Warren, Douglas, Harlan, Brennan, Stewart, White, Fortas
  • Dissenting: Justice Black
  • Ruling: Wiretapping a phone booth qualifies as a “search and seizure” under the Fourth Amendment. Police should have obtained a warrant prior to wiretapping the phone booth that Katz used.

Facts of the Case

On February 4, 1965, agents from the Federal Bureau of Investigation began surveilling Charles Katz. They suspected him of playing a role in an illegal gambling operation. Over the course of two weeks, they observed him frequently using a public payphone and believed he was transmitting information to a known gambler in Massachusetts. They confirmed their suspicions by obtaining a record of the numbers he called while using the phone booth. Agents taped a recorder and two microphones to the outside of the booth. After Katz left the booth, they removed the device and transcribed the recordings. Katz was arrested on eight counts which included illegal transmission of wagering information across state lines.

At trial, the court allowed the tapes of Katz’s conversation to be admitted into evidence. After the non-jury trial, Katz was convicted on all eight counts. On June 21, 1965 he was sentenced to a fine of $300. He appealed the decision, but the appeals court affirmed the district court’s judgment.

Constitutional Questions

The Fourth Amendment states that people have the right, “to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.” The Fourth Amendment protects more than just physical property. It protects things that aren’t tangible, like conversations.

Does the use of a wiretap to listen in on a private conversation in a public phone booth violate the Fourth Amendment? Is physical intrusion necessary to demonstrate that a search and seizure has occurred?


Attorneys representing Katz argued that the phone booth was a “constitutionally protected area” and officers physically penetrated this area by placing a listening device on it. That device then allowed officers to listen in on Katz’s conversation, a clear violation of his right to privacy. When officers physically intruded on the phone booth, their actions qualified as a search and seizure. Therefore, the attorneys argued, the agents violated Katz’s Fourth Amendment protection against unlawful searches and seizures.

Attorneys on behalf of the government noted that although Katz was having what he believed to be a private conversation, he was speaking in a public space. A phone booth is an inherently public space and cannot be considered a “constitutionally protected area,” the attorneys argued. The booth was made partly of glass, meaning that the officers could see the defendant while inside the booth. Police did nothing more than listen to a nearby conversation taking place on a public sidewalk. Their actions did not require a search warrant, the attorneys argued, because the agents did not physically intrude on Katz’s privacy.

Majority Opinion

Justice Stewart delivered the 7-1 decision in favor of Katz. Whether or not police physically intruded upon a “constitutionally protected area” is irrelevant to the case, Justice Stewart wrote. What matters is whether Katz had a reasonable belief that his phone call would be private inside the booth. The Fourth Amendment “protects people not places,” Justice Stewart argued.

Justice Stewart wrote:

“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,” Justice Stewart wrote.

He added that it was clear the officers had “acted with restraint” when electronically surveilling Katz. However, that restraint was a decision made by the officers themselves, not a judge. Based on the evidence, a judge could have constitutionally authorized the exact search that took place, Justice Stewart wrote. A judicial order could have accommodated the “legitimate needs” of the police while ensuring that Katz’s Fourth Amendment rights were protected. Judges act as an important safeguard when it comes to the constitutionality of searches and seizures, Justice Stewart wrote. In this case, officers conducted a search without even attempting to secure a search warrant.

Dissenting Opinion

Justice Black dissented. He argued first that the Court’s decision was too broad and took too much meaning away from the Fourth Amendment. In Justice Black’s opinion, wiretapping was closely related to eavesdropping. Forcing officers to obtain a warrant in order to “overhear future conversations” was not only unreasonable but inconsistent with the intent of the Fourth Amendment, he argued. 

Justice Black wrote:

“There can be no doubt that the Framers were aware of this practice, and if they had desired to outlaw or restrict the use of evidence obtained by eavesdropping, I believe that they would have used the appropriate language to do so in the Fourth Amendment.”

He added that the Court should have followed precedent set by two prior cases, Olmstead v. United States (1928) and Goldman v. United States (1942). These cases were still relevant and had not been overruled. Justice Black alleged that the Court was slowly “rewriting” the Fourth Amendment to apply to an individual’s privacy and not just unreasonable searches and seizures.


Katz v. United laid the groundwork for the “reasonable expectation of privacy” test that is still used today when determining whether police needed a warrant in order to conduct a search. Katz extended protections against unreasonable searches and seizures to electronic wiretapping devices. Most importantly, the Court acknowledged the evolution of technology and the need for greater privacy protections.


  • Katz v. United States, 389 U.S. 347 (1967).
  • Olmstead v. United States, 277 U.S. 438 (1928).
  • Kerr, Orin S. “Four Models of Fourth Amendment Protection.” Stanford Law Review, vol. 60, no. 2, Nov. 2007, pp. 503–552., http://www.stanfordlawreview.org/wp-content/uploads/sites/3/2010/04/Kerr.pdf.
  • “If These Walls Could Talk: The Smart Home and the Fourth Amendment Limits of the Third Party Doctrine.” Harvard Law Review, vol. 30, no. 7, 9 May 2017, https://harvardlawreview.org/2017/05/if-these-walls-could-talk-the-smart-home-and-the-fourth-amendment-limits-of-the-third-party-doctrine/.
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Spitzer, Elianna. "Katz v. United States: Supreme Court Case, Arguments, Impact." ThoughtCo, Aug. 29, 2020, thoughtco.com/katz-v-united-states-supreme-court-case-arguments-impact-4797888. Spitzer, Elianna. (2020, August 29). Katz v. United States: Supreme Court Case, Arguments, Impact. Retrieved from https://www.thoughtco.com/katz-v-united-states-supreme-court-case-arguments-impact-4797888 Spitzer, Elianna. "Katz v. United States: Supreme Court Case, Arguments, Impact." ThoughtCo. https://www.thoughtco.com/katz-v-united-states-supreme-court-case-arguments-impact-4797888 (accessed June 5, 2023).