In the case of Danny Lee Kyllo v. United States, 2000, the Supreme Court ruled that using a thermal imaging device from outside to detect relative amounts of heat within a private home constituted a search under the Fourth Amendment. The police had used this technology to suspect Kyllo was growing marijuana in his house due to high-intensity lamps typically used for indoor growth. This information led them to obtain a warrant and find over 100 plants inside his home. However, Justice Scalia delivered an opinion stating that obtaining any details from inside a person's home that could not otherwise have been obtained without physical intrusion is presumptively unreasonable without a warrant - regardless if it was through sense-enhancing technology or not. Therefore, since no search warrant was initially issued before using thermal imaging on Kyllo’s residence, all subsequent evidence gathered became invalid leading to overturning his conviction.

In the dissenting opinion for Danny Lee Kyllo v. United States, Justice John Paul Stevens argued that the use of thermal imaging technology by law enforcement did not constitute a "search" under the Fourth Amendment. He contended that since any person could technically detect heat emissions from a house without physically intruding into it, such observations should not be considered as invasions of privacy. Furthermore, he pointed out that this technology does not reveal specific activities happening inside but only vague inferences about excessive heat which could be due to various innocent reasons like saunas or hot tubs and hence doesn't invade personal privacy in an intrusive manner. Therefore, according to him, no warrant was required for using thermal imagers outside homes.