In a 9-0 decision, the Supreme Court held that attaching a GPS device to a vehicle, and using it to monitor the vehicle’s movements on public streets, constitutes a search under the Fourth Amendment. As a result, the Court held it is unconstitutional to attach a GPS device to a vehicle without a warrant or consent.
The case started after the FBI obtained a warrant, but the warrant only authorized installation of the device in the District of Columbia and within 10 days of when the warrant was issued. Instead, agents installed the device on the 11th day and in Maryland. Consequently, the Court treated the case as though there was no warrant.
The agents tracked the vehicle’s movements for 28 days. Later, they secured an indictment of the defendant and others on drug trafficking conspiracy charges based in part on evidence obtained with the GPS device. The District Court suppressed the GPS data obtained while the vehicle was parked at the Defendant's residence, but decided the remaining data was admissible because the Defendant had no reasonable expectation of privacy when the vehicle was on public streets. The Defendant was convicted and appealed.
Justice Scalia, writing for the majority, reasoned one's vehicle is a type of personal "effect" the Fourth Amendment specifically mentions, and that, therefore, attaching a GPS device to one's vehicle is the type of encroachment that would count as a search under the Fourth Amendment at the time it was adopted. The Fourth Amendment protects the “right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.” Justices Roberts, Kennedy, Thomas and Sotomayor joined his opinion.
Justice Alito wrote an opinion reaching the same result from a different perspective. He decided the use of the GPS device was unconstitutional because the length of the monitoring made it a degree of intrusion that a reasonable person would not have anticipated. Justices Kagan, Ginsburg, and Breyer joined his opinion.