Law enforcement must obtain a warrant before attaching GPS trackers to suspects’ vehicles, a federal appeals court ruled this week.

The decision resolved a legal question left unanswered after the U.S. Supreme Court ruled in 2012 (United States v. Jones - pdf) that police violated a suspect’s Fourth Amendment rights by putting a GPS device on his vehicle. The high court declined to rule at the time whether such a search was unreasonable and had required a warrant.

In a 2-1 decision, judges with the Third Circuit Court of Appeals ruled on Tuesday that police do need to obtain a warrant before using GPS trackers. The ruling came in U.S. vs. Harry Katzin, Michael Katzin and Mark Katzin (pdf), in which the Federal Bureau of Investigation affixed a “slap-on” GPS tracker to the car of Harry Katzin, who was suspected of helping rob multiple pharmacies in Delaware, Maryland and New Jersey.

The government argued that having to obtain a warrant would undermine law enforcement’s ability to investigate criminal wrongdoing. This, too, was rejected in the justices’ ruling.

“Consequently, we hold that — absent some highly specific circumstances not present in this case — the police cannot justify a warrantless GPS search with reasonable suspicion alone,” the justices wrote.

“Today’s decision is a victory for all Americans because it ensures that the police cannot use powerful tracking technology without court supervision and a good reason to believe it will turn up evidence of wrongdoing,” ACLU attorney Catherine Crump said in a statement. “These protections are important because where people go reveals a great deal about them, from who their friends are, where they visit the doctor and where they choose to worship.”

-Noel Brinkerhoff

To Learn More:

Court Rules Probable-Cause Warrant Required for GPS Trackers (by Kim Zetter, Wired)

U.S. v. Katzin – Opinion (American Civil Liberties Union)

United States of America v. Harry Katzin, Michael Katzin, and Mark Katzin (U.S. Court of Appeals for the Third Circuit) (pdf)

Despite Supreme Court Decision, Obama Administration Insists GPS Tracking Doesn’t Require Warrant (by Danny Biederman and Noel Brinkerhoff, AllGov)