A new ruling issued by the U.S. Supreme Court makes clear that law enforcement agencies need to obtain a search warrant before they can attach a GPS tracking device onto a person's automobile. The unanimous decision, released on Jan. 23, upheld a decision of the U.S. Court of Appeals for the D.C. Circuit, which had held that evidence gathered against an alleged drug dealer through a tracking device placed in his Jeep was illegal under the Fourth Amendment's search and seizure clause.

Authorities had obtained a warrant prior to implanting the device, but by the time they actually put it in the Jeep, the warrant had expired. Still, they used the device to keep track of where the defendant's car was being driven for 28 days, and at trial used those movements as evidence against him.

Justice Antonin Scalia wrote the Court's decision. Without addressing the constitutionality of the electronic monitoring without a warrant, the decision said the act of the warrantless implantation of the device "constitutes a 'search'" under the Fourth Amendment, which prohibits unreasonable searches and seizures, generally including warrantless searches of suspects. Therefore, the evidence gathered as a result of the implantation should not have been allowed at trial, Scalia said.

The case raised questions of the right to privacy in an age of the government's increasing ability to monitor citizens with ever-evolving technology. In a concurring opinion, Justice Samuel Alito wished that the Court had ruled on the question of the legality of the monitoring. Justice Sonia Sotomayor agreed in her concurrence, but noted that the justices had resolved the relatively narrow legal question before it.

Source: Washington Post, "Supreme Court: Warrants needed in GPS tracking," Robert Barnes, Jan. 23, 2012