The GPS device helped authorities link Washington, D.C., nightclub owner Antoine Jones to a suburban house used to stash money and drugs. He was sentenced to life in prison before the appeals court overturned the conviction.
Associate Justice Antonin Scalia said that the government's installation of a GPS device, and its use to monitor the vehicle's movements, constitutes a search, meaning that a warrant is required.
"By attaching the device to the Jeep" that Jones was using, "officers encroached on a protected area," Scalia wrote.
All nine justices agreed that the placement of the GPS on the Jeep violated the Fourth Amendment's protection against unreasonable search and seizure.
Scalia wrote the main opinion of three in the case. He was joined by Chief Justice John Roberts and Justices Anthony Kennedy, Clarence Thomas and Sonia Sotomayor.
Sotomayor also wrote one of the two concurring opinions that agreed with the outcome in the Jones case for different reasons.
Justice Samuel Alito also wrote a concurring opinion in which he said the court should have gone further and dealt with GPS tracking of wireless devices, like mobile phones. He was joined by Justices Ruth Bader Ginsburg, Stephen Breyer and Elena Kagan.
A federal appeals court in Washington had overturned Jones's drug conspiracy conviction because police did not have a warrant when they installed a GPS device on his vehicle and then tracked his movements for a month. The Supreme Court agreed with the appeals court.
