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Katz v. United States

Can a personal expectation of privacy challenge the Fourth Amendment?


Docket: 35

Date Argued: October 17, 1967

Date Decided: December 18, 1967

When Charles Katz was suspected of transmitting gambling information across states, federal agents took action, attaching a recording device to the outside of a phone booth that was being used by Katz. Upon reviewing the conversation, the court held that Katz was indeed guilty. Katz, however, challenged this decision, claiming that the use of the recording device was an infringement on his privacy and a violation of his Fourth Amendment right to be protected from unreasonable searches and seizures. Despite the Ninth Circuit’s Court of Appeals reaffirming the court's holding, Katz and his attorneys continued challenging this notion until they found themselves at the Supreme Court.

PRESIDING QUESTIONS: Did the usage of the recording device to monitor Katz’s conversation need a search warrant? Is physical intrusion the only form of search or seizure? Does the Fourth Amendment protect people or places?


Side 1 - Charles Katz (Petitioner)

  • Charles Katz was a sports bettor in Los Angeles, California who was being charged with 8 counts for his interstate gambling operations.

  • Petitioner Argument: (Majority) The usage of an eavesdropping device to monitor Katz’s conversation was a violation of both his privacy and his Fourth Amendment rights.

Side 2 - United States (Respondent)

  • Respondent Argument: (Dissenting) The Fourth Amendment does not encompass telephone wires, there was no search and seizure of tangible items, and the area was public and therefore not protected under the heightened Fourth Amendment protections that a private area, like a house, would be subjected to..

Ruling - 7-1 Majority Opinion Decision for Katz

  • The recording of Katz’s conversation was unconstitutional. Since Katz had a reasonable expectation of privacy inside the phone booth, obstructing that expectation was a search and seizure under the Fourth Amendment. The court also held that the Fourth Amendment’s protections extend beyond physical items and can be applied to verbal statements as well. The court propounded that since the Constitution protects the individual rights of people, physical intrusion is not a key component of searches and seizures.

Concurring Opinion

  • Justice John Marshall Harlan penned the “Katz test,” a notable two-part assessment that has become more popular than the case it stemmed from. The reason behind Harlan’s concurring opinion was that he felt the need to elaborate on the real meaning behind the majority opinion. He argued that his interpretation of the opinion was that the Fourth Amendment protects a person’s privacy, and his test included two prongs:

  1. A person must demonstrate a subjective reasonable expectation of privacy

  2. Society as a whole must recognize this expectation as reasonable

  • The Supreme Court adopted this as a key part of search analysis in 1979 with the case Smith v. Maryland: in that case the use of a pen register (a device that records all numbers called from a telephone line) to track the defendan’ts calls was not a violation of the defendant’s Fourth Amendment rights since the defendant could not have fulfilled the first prong of the Katz test because they cannot have a reasonable expectation of privacy concerning something that they share with a third party willingly (the telephone company).


The Constitution is an influential, distinguished document that still shapes and affects American society over 200 years after its ratification. However, contrary to popular belief, it is not a static, rigid document, but rather a flexible testament to the nation’s ideals. Katz v. United States is an exemplary example of this, as it changed the way the courts view the Fourth Amendment.

Katz’s appeal to the courts to reconsider the ruling against him effectively challenged a precedent set by Olmstead v. United States (1928). In this case, it was held that wiretapping does not count as a search or seizure, which are physical intrusions of a person’s materials. Katz v. United States also effectively demonstrates how amendments can adapt to modern technological advances. When the Fourth Amendment was written, technology wasn’t nearly as advanced as it is today, so it only makes sense for the responsibilities of the amendment to adjust to allow for recent modern advancements.

The case also puts into question whether or not a privacy amendment should be added to the Constitution. While amendments do implicitly grant all citizens privacies of religion, home, searches and seizures, and property (in the First, Third, Fourth, and Fifth amendments, respectively), there is no one amendment that explicitly outlines a fundamental right to privacy for all citizens. By redefining what a search and seizure constitutes and highlighting the importance of privacy in a modern, interconnected world, Katz v. United States establishes itself as a landmark case in United States history.




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