Thermal Marijuana Dynamics

Facts

In 1991, Agent William Elliott of the United States Department of the Interior suspected that Danny Kyllo (petitioner) was growing marijuana in his home, part of a triplex on Rhododendron Drive in Florence, Oregon. Indoor marijuana growth typically requires high- intensity lamps. In order to determine whether an amount of heat was emanating from the petitioner's home consis- tent with the use of such lamps, at 3:20 A.M. on January 16, 1992, Agent Elliott and Dan Haas used an Agema Thermovision 210 thermal imager to scan the triplex.

Thermal imagers convert radiation into images based on relative warmth-black is cool, white is hot, shades of gray connote relative differences; in that re- spect, it operates somewhat like a video camera show- ing heat images.

The scan of Mr. Kyllo's home was performed from the passenger seat of Agent Elliott's vehicle across the street from the front of the house and also from the street in back of the house. The scan showed that the roof over the garage and a side wall of Mr. Kyllo's home were relatively hot compared to the rest of the home and substantially warmer than neighboring homes in the triplex. Agent Elliott concluded that Mr. Kyllo was using halide lights to grow marijuana in his house, which indeed he was. Based on tips from informants, utility bills, and the thermal imaging, a federal magis- trate judge issued a warrant authorizing a search of Mr. Kyllo's home, and the agents found an indoor grow- ing operation involving more than 100 plants. Mr. Kyllo was indicted on one count of manufacturing marijuana. Mr. Kyllo unsuccessfully moved to suppress the evi- dence seized from his home and then entered a condi- tional guilty plea.The Court of Appeals for the Ninth Circuit re- manded the case. On remand the District Court upheld the validity of the warrant. A divided Court of Appeals initially reversed, but that opinion was withdrawn and the panel affirmed. Mr. Kyllo appealed.

Judicial Opinion

SCALIA, Justice

This case presents the question whether the use of a thermal-imaging device aimed at a private home  from a public street to detect relative amounts of heat within the home constitutes a "search" within the meaning of the Fourth Amendment.

The permissibility of ordinary visual surveillance of a home used to be clear because, well into the 20th cen- tury, our Fourth Amendment jurisprudence was tied to common-law trespass. Visual surveillance was unquestionably lawful because "'the eye cannot by the laws of England be guilty of a trespass.'" "[T]he Fourth Amendment protection of the home has never been extended to require law enforcement officers to shield their eyes when passing by a home on public thoroughfares."

The present case involves officers on a public street engaged in more than naked-eye surveillance of a home. We have previously reserved judgment as to how much technological enhancement of ordinary percep- tion from such a vantage point, if any, is too much. While we upheld enhanced aerial photography of an in- dustrial complex in Dow Chemical [see Case 7.4], we noted that we found "it important that this is not an area immediately adjacent to a private home, where privacy expectations are most heightened. . . .

[I]n the case of the search of the interior of homes- the prototypical and hence most commonly litigated area of protected privacy-there is a ready criterion, with roots deep in the common law, of the minimal ex- pectation of privacy that exists, and that is acknowl- edged to be reasonable. We think that obtaining by sense-enhancing technology any information regarding the interior of the home that could not otherwise have been obtained without physical "intrusion into a consti- tutionally protected area," constitutes a search-at least where (as here) the technology in question is not in gen- eral public use. The fact that equivalent information could sometimes be obtained by other means does not make lawful the use of means that violate the Fourth Amendment. The police might, for example, learn how many people are in a particular house by setting up year-round surveillance; but that does not make break- ing and entering to find out the same information law- ful. In any event, on the night of January 16, 1992, no outside observer could have discerned the relative heat of Kyllo's home without thermal imaging.

The dissent makes this its leading point, contending that there is a fundamental difference between what it calls "off-the-wall" observations and "through-the-wall surveillance." But just as a thermal imager captures only heat emanating from a house, so also a powerful directional microphone picks up only sound emanating from a house-and a satellite capable of scanning from many miles away would pick up only visible light ema- nating from a house. We rejected such a mechanical in- terpretation of the Fourth Amendment. Reversing that approach would leave the homeowner at the mercy of advancing technology-including imaging  technology

that could discern all human activity in the home. The rule we adopt must take account of more sophisticated systems that are already in use or in development.

We have said that the Fourth Amendment draws "a firm line at the entrance to the house." That line, we think, must be not only firm but also bright-which requires clear specification of those methods of surveil- lance that require a warrant. While it is certainly possible to conclude from the videotape of the thermal imaging that occurred in this case that no "significant" compromise of the homeowner's privacy has occurred, we must take the long view, from the original meaning of the Fourth Amendment forward.

Where, 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.

Reversed.

Case Questions

1.  What would be the difference between thermal scanning and, for example, observing with the human eye patches of snow on a roof with some areas showing more melting than others?

2.  Given the development of cell phones and conver- sation held in public places, what are the rules for warrants and listening to phone conversations?

3.  Does the method of invasion of privacy make a dif- ference in determining whether there is a Fourth Amendment violation?