About: Kyllo v. United States

Kyllo v. United States, 533 U.S. 27 (2001), was a decision by the Supreme Court of the United States in which the court ruled that the use of thermal imaging devices to monitor heat radiation in or around a person's home, even if conducted from a public vantage point, is unconstitutional without a search warrant. In its majority opinion, the court held that thermal imaging constitutes a "search" under the Fourth Amendment, as the police were using devices to "explore details of the home that would previously have been unknowable without physical intrusion." The ruling has been noted for refining the reasonable expectation of privacy doctrine in light of new surveillance technologies, and when those are used in areas that are accessible to the public.