Supreme Court rules 7-1 that the 4th Amendment protects people, not places — Harlan's concurrence establishes the "reasonable expectation of privacy" test governing all electronic surveillance

The Supreme Court ruled 7-1 on December 18, 1967, that the FBI's warrantless electronic surveillance of Charles Katz violated the 4th Amendment. Justice Stewart's majority overruled the trespass doctrine from Olmstead (1928), holding "the 4th Amendment protects people, not places." Justice Harlan's concurrence introduced the two-pronged "reasonable expectation of privacy" test: the person must have a subjective expectation of privacy that society recognizes as objectively reasonable. Congress responded six months later with the Wiretap Act (Title III of the 1968 Crime Control Act), establishing the first federal warrant procedure for electronic surveillance. Justice Black dissented alone, arguing the 4th Amendment's plain text covered only physical searches.