Bumper cop: warrantless GPS tracking.

• Author: Sullum, Jacob
• Position: Brief article

IF POLICE do not need a warrant to observe someone in public places, does that mean they do not need a warrant when they use a GPS device to track his car? The Supreme Court is considering that question in a case involving a Washington, D.C., nightclub owner who was convicted of conspiring to sell cocaine and sentenced to life in prison based largely on information about his movements collected via a GPS tracker that police surreptitiously attached to his Jeep.

When the U.S. Court of Appeals for the D.C. Circuit overturned the conviction in 2009,Judge Douglas Ginsburg said GPS tracking is qualitatively different from the sort of warrantless public surveillance the Supreme Court has allowed. "A person who knows all of another's travels," Ginsburg wrote, "can deduce whether he is a weekly church goer, a heavy drinker, a regular at the gym, an unfaithful husband, an outpatient...