Kyllo v. United States


Upon suspicion that the defendant was growing marijuana in his home, police used a thermal-imaging device to detect heat radiating from the defendant’s home. With this information, police obtained a search warrant for the home.


Does the use of a thermal-imaging device to detect relative amounts of heat emanating from a private home constitute an unconstitutional search in violation of the Fourth Amendment?


Yes. In a 5-4 opinion delivered by Justice Antonin Scalia, the Court held that [w]here, as here, the Government uses a device that is not in general public use, to explore details of the home that would previously have been unknowable without physical intrusion, the surveillance is a ‘search’ and is presumptively unreasonable without a warrant.” In dissent, Justice John Paul Stevens argued that the “observations were made with a fairly primitive thermal imager that gathered data exposed on the outside of [Kyllo’s] home but did not invade any constitutionally protected interest in privacy,” and were, thus, “information in the public domain.


The Fourth Amendment of the Constitution protects persons and their property from unreasonable searches by the government. The home is one place where society deems an expectation of privacy reasonable. In order to preserve this degree of privacy, government searches under these circumstances must be supported by a warrant.
The Fourth Amendment protections are not conditional upon the quality of information obtained by the government. So long as there is a subjective expectation of privacy and society is willing to recognize this expectation as reasonable, the government must obtain a warrant before conducting a search.

Michael R. Dreeben Department of Justice, argued the cause for the United States, Kenneth Lerner Argued the cause for the petitioner
Kyllo’s Home
United States
Rehnquist Court
533 US 27 (2001)
Feb 20, 2001
Jun 11, 2001