FOURTH AMENDMENT [U.S. Constitution] - 'The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.'
"The Fourth Amendment governs not only the seizure of tangible items but extends as well to the recording of oral statements."
From Katz v U.S.