As technology continues to develop, the Court has had to consider new methods of investigation by law enforcement officials. In
Kyllo v. United States, 533 U.S. 27, 121 S. Ct. 2035, 150 L. Ed. 2d 94 (2001), the Court considered the constitutionality of the use of a thermal imaging device during surveillance of a home. An agent of the U.S.
Interior Department suspected that the defendant, Danny Kyllo, was growing marijuana in his home. The officer knew that indoor marijuana growth requires use of high-intensity lamps, and the officer sought to discover the presence of these lamps through the use of the thermal imaging device. The device demonstrated that the defendant was likely using a high-intensity lamp, and the agent then sought a
Search Warrant from a federal magistrate judge. A subsequent search of the home discovered marijuana.
The Supreme Court, per Justice
Antonin Scalia, found that the use of the device to survey the inside of the defendants home constituted a "search" for Fourth Amendment purposes. The government argued that because the device only sensed heat emanating from the exterior of the house, use of the device was not an unlawful intrusion on the defendant.
Scalia disagreed, noting that Katz forbids a mechanical application of the Fourth Amendment that focuses only upon the physical capability of a surveillance device. He noted, "Reversing that approach [in Katz] would leave the homeowner at the mercy of advancing technology—including imaging technology that could discern all human activity in the home." Because the agent had not obtained a warrant until after he conducted a search of Kyllo's home, the search violated Kyllo's Fourth Amendment rights.