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Katz v. United States, 389 U.S. 347 (1967), was a landmark United States Supreme Court case discussing the nature of the "right to privacy" and the legal definition of a "search" of intangible property, such as electronic-based communications like telephone calls.[1] The Court's ruling refined previous interpretations of the unreasonable search and seizure clause of the Fourth Amendment to count immaterial intrusion with technology as a search, overruling Olmstead v. United States and Goldman v. United States. Katz also extended Fourth Amendment protection to all areas via the "Katz test" to determine when a person has a "reasonable expectation of privacy". The Katz test has been used in numerous cases, particularly with the advancement of technology that pose new questions on expectations of privacy.[2]

Katz v. United States
Seal of the United States Supreme Court
Argued October 17, 1967
Decided December 18, 1967
Full case nameCharles Katz v. United States
Citations389 U.S. 347 (more)
88 S. Ct. 507; 19 L. Ed. 2d 576; 1967 U.S. LEXIS 2
Case history
Prior369 F.2d 130 (9th Cir. 1966); cert. granted, 386 U.S. 954 (1967).
The Court extended the Fourth Amendment protection from unreasonable search and seizure to protect individuals with a "reasonable expectation of privacy."
Court membership
Chief Justice
Earl Warren
Associate Justices
Hugo Black · William O. Douglas
John M. Harlan II · William J. Brennan Jr.
Potter Stewart · Byron White
Abe Fortas · Thurgood Marshall
Case opinions
MajorityStewart, joined by Warren, Douglas, Harlan, Brennan, White, Fortas
ConcurrenceDouglas, joined by Brennan
Marshall took no part in the consideration or decision of the case.
Laws applied
U.S. Const. amend. IV
This case overturned a previous ruling or rulings
Olmstead v. United States (1928)



Charles Katz used a public pay phone booth to transmit illegal gambling wagers from Los Angeles to Miami and Boston. Unbeknownst to Katz, the FBI was recording his conversations via an electronic eavesdropping device attached to the exterior of the phone booth. Katz was convicted based on these recordings. He challenged his conviction, arguing that the recordings were obtained in violation of his Fourth Amendment rights. The Court of Appeals sided with the FBI because there was no physical intrusion into the phone booth itself.[3]

Constitutional issues of the caseEdit

  • Does the right to privacy extend to telephone booths and other public places?
  • Is a physical intrusion necessary to constitute a search?


  • "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." – Justice Stewart[4]
  • Regardless of the location, a conversation is protected from unreasonable search and seizure under the Fourth Amendment if it is made with a "reasonable expectation of privacy".
  • Wiretapping counts as a search (physical intrusion is not necessary).

Decision and rationaleEdit

The Court ruled 7–1 in favor of Katz, with Justice Black in dissent. Justice Marshall did not participate in the vote. Writing for the majority, Justice Stewart wrote, "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."[4] Certain details, such as shutting the door on the telephone booth, help determine if a person intends for a conversation to be private. Thus, private conversations can be made in public areas.

Justice Harlan's concurring opinion summarizes the essential holdings of the majority:

(a) that an enclosed telephone booth is an area where, like a home, and unlike a field, a person has a constitutionally protected reasonable expectation of privacy; (b) that electronic as well as physical intrusion into a place that is in this sense private may constitute a violation of the Fourth Amendment; and (c) that an invasion of a constitutionally protected area by federal authorities is, as the Court has long held, presumptively unreasonable in the absence of a search warrant.[4]

The majority opinion by Justice Stewart did not dispute that a magistrate "could constitutionally have authorized" the wiretap in this case, but, since such a warrant was neither sought nor obtained, the search was therefore unconstitutional.[5] Likewise, the Court said it was not recognizing any general right to privacy in the Fourth Amendment: "the protection of a person's general right to privacy—his right to be let alone by other people—is, like the protection of his property and of his very life, left largely to the law of the individual States."[6]

The Katz case made government wiretapping by both state and federal authorities subject to the Fourth Amendment's warrant requirements.[7]

Justice Harlan's concurrenceEdit

In a concurring opinion, Justice Harlan built upon the foundations of the majority opinion and formulated the "reasonable expectation" test for determining if a person should expect privacy in a given location. Harlan's test, not the majority opinion, is the most common formulation cited by courts. Later, this test was arranged into a two prong test for assessing the reasonableness of an expectation of privacy: If (1) the individual "has exhibited an actual (subjective) expectation of privacy", and (2) society is prepared to recognize that this expectation is (objectively) reasonable, then there is a right of privacy in the given circumstance.[8] This test was adopted by the majority in Smith v. Maryland (1979).[9] Harlan basically breaks down what this ruling means for future cases involving search and seizures.

Justice Black's dissentEdit

In his case, Hugo Black argued that the Fourth Amendment, as a whole, was only meant to protect "things" from physical search and seizure; it was not meant to protect personal privacy. Additionally, Black argued that the modern act of wiretapping was analogous to the act of eavesdropping, which was around even when the Bill of Rights was drafted. Black concluded that if the drafters of the Fourth Amendment had meant for it to protect against eavesdropping they would have included the proper language.

See alsoEdit


  1. ^ Katz v. United States, 389 U.S. 347 (1967).
  2. ^ Tokson, Mathew (2016). "KNOWLEDGE AND FOURTH AMENDMENT PRIVACY". Northwestern University Law Review.
  3. ^ Katz v. United States, 369 F.2d 130 (9th Cir. 1966).
  4. ^ a b c White, Welsh S., and James J. Tomkovicz. Criminal Procedure: Constitutional Constraints upon Investigation and Proof. Newark, NJ: LexisNexis Matthew Bender, 2004. (p. 6).
  5. ^ Schroeder, Steve (2012). The Lure: The True Story of How the Department of Justice Brought Down Two of the World's Most Dangerous Cyber Criminals. Cengage Learning. p. 127.
  6. ^ Morgan, Candace (2010). "Challenges and Issues Today". Intellectual Freedom Manual. American Library Association, Office for Intellectual Freedom. pp. 41–42.
  7. ^ Friedman, Leon (1978). The Justices of the United States Supreme Court: Their Lives and Major Opinions. V. Chelsea House. p. 292.
  8. ^ Freiwald, Susan (2007). "First Principles of Communications Privacy". Stanford Technology Law Review (3).
  9. ^ Smith v. Maryland, 442 U.S. 735 (1979).

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