Facts of the Case

Acting on a suspicion that Katz was transmitting gambling information over the phone to clients in other states, Federal agents attached an eavesdropping device to the outside of a public phone booth used by Katz. Based on recordings of his end of the conversations, Katz was convicted under an eight-count indictment for the illegal transmission of wagering information from Los Angeles to Boston and Miami. On appeal, Katz challanged his conviction arguing that the recordings could not be used as evidence against him. The Court of Appeals rejected this point, noting the absence of a physical intrusion into the phone booth itself. The Court granted certiorari.

Question

Does the Fourth Amendment protection against unreasonable searches and seizures require the police to obtain a search warrant in order to wiretap a public pay phone?

Conclusion

Yes. The Court ruled that Katz was entitled to Fourth Amendment protection for his conversations and that a physical intrusion into the area he occupied was unnecessary to bring the Amendment into play. "The Fourth Amendment protects people, not places," wrote Justice Potter Stewart for the Court. A concurring opinion by John Marshall Harlan introduced the idea of a 'reasonable' expectation of Fourth Amendment protection.