Kyllo v. United States, , held that the use of a thermal imaging device from a public vantage point to monitor the radiation of heat from a person's home was a "search" within the meaning of the Fourth Amendment

Fourth Amendment to the United States Constitution

The Fourth Amendment to the United States Constitution is the part of the Bill of Rights which guards against unreasonable searches and seizures, along with requiring any warrant to be judicially sanctioned and supported by probable cause...

, and thus required a warrant. Because the police in this case did not have a warrant, the Court reversed Kyllo's conviction for growing marijuana.
Department of the Interior used a thermal imaging device outside of Danny Lee Kyllo's home.