An alleged D.C. drug dealer who had a conviction overturned in a landmark Supreme Court ruling emerged partially victorious yesterday when a judge declared a mistrial in the case against him.

In a case that stemmed from an investigation by D.C. police and the FBI of a local drug dealer, the U.S. Supreme Court ruled unanimously today that police across the country need a warrant if they want to track suspects using GPS monitors.

It’s the first Monday in October, and that means that the U.S. Supreme Court gets back to work hearing cases today. On its docket this term is a case involving a D.C. man, GPS surveillance and the question of how far is too far in tracking a suspect.