What was the main outcome of Katz v. United States?

The main outcome of Katz v. United States was a significant expansion of Fourth Amendment rights, which protect individuals against unreasonable searches and seizures. In this landmark ruling, the Supreme Court established that the Fourth Amendment's protections extend beyond physical intrusions into a person’s property; it also protects individuals’ reasonable expectation of privacy.

In this case, the Court ruled that the FBI’s use of a listening device to monitor Katz’s phone calls without a warrant constituted a violation of his Fourth Amendment rights. The decision underscored that privacy must be respected in public spaces as well as private, thereby broadening the scope of what constitutes a “search” and reinforcing the idea that a warrant is generally required for such investigative actions, regardless of the method employed.