Katz v United States

Katz v United States is a 1967 decision of the United States Supreme Court that redefined the scope of Fourth Amendment privacy protection. Federal Bureau of Investigation agents attached a listening device to the outside of a public telephone booth that Katz used to transmit illegal gambling wagers, recording his conversations without a warrant. The Court held that the Fourth Amendment protects people rather than simply places, so a warrantless recording of a conversation Katz reasonably expected to remain private violated the Constitution even though the agents never physically entered the booth. The decision replaced an older test based on physical trespass with the reasonable expectation of privacy standard that still governs most Fourth Amendment search analysis today.