Kyllo v. United States
Citation
533 U.S. 27 (2001). Supreme Court of the United States.
Facts
Federal agents suspected Danny Kyllo of growing marijuana in his home. Without a warrant, they used a thermal imaging device from the street to detect heat signatures emanating from the home consistent with high-intensity grow lights. Based in part on the thermal scan, agents obtained a search warrant and found marijuana plants. Kyllo moved to suppress.
Issue
Is the warrantless use of a thermal imaging device directed at a private home to detect activities inside a Fourth Amendment search?
Holding
The Court held that using sense-enhancing technology not in general public use to obtain information about the interior of a home that would previously have been unknowable without physical intrusion constitutes a search within the meaning of the Fourth Amendment and requires a warrant.
Rule / Doctrine
The home is the core of Fourth Amendment protection. Where the government uses technology not in general public use to explore the details of a home that would be otherwise unknowable, surveillance is a search — regardless of whether the officer physically enters. The rule is keyed to two limitations: the technology must not be in general public use, and the surveillance must reveal interior details. Katz v. United States’ reasonable expectation of privacy is strongest in the home.
Significance
Kyllo established an important principle for the technology age: the Fourth Amendment’s protection of the home cannot be eroded by new surveillance devices. The “general public use” caveat, however, raises questions about whether more widely adopted technologies (e.g., commercial thermal cameras) would still require a warrant. The case preceded United States v. Jones and Carpenter v. United States in the Court’s evolving treatment of technology and privacy.