In United States v. Knotts, 460 U. S. 276 (1983), the court held that the warrantless monitoring of an electronic tracking device ('beeper') inside a container of chemicals did not violate the Fourth Amendment when it revealed no information that could not have been obtained through visual surveillance. Left unresolved in Knotts was (1) whether installation of a beeper in a container of chemicals with the consent of the original owner constitutes a search or seizure within the meaning of the Fourth Amendment when the container is delivered to a buyer having no knowledge of the presence of the beeper, and (2) whether monitoring of a beeper falls within the ambit of the Fourth Amendment when it reveals information that could not have been obtained through visual surveillance.
Searches and seizures inside a home without a warrant are presumptively unreasonable absent exigent circumstances. Where, without a warrant, the Government surreptitiously employs an electronic device to obtain information that it could not have obtained by observation from outside the curtilage of the house. The beeper tells the agent that a particular article is actually located at a particular time in the private residence and is in the ...