What started out as a case against a man accused of violently robbing a handful of restaurants and gas stations has morphed into a landmark court privacy decision about cell phone location tracking.

The 11th US Circuit Court of Appeals unanimously ruled (PDF) on Wednesday that police must obtain a warrant to track mobile users' location data. This means cell phone carriers are not obliged to hand over users' location history to police unless a warrant in produced.

The original case that led to this decision involved a man named Quartavius Davis who was convicted by a jury for taking part in a string of armed robberies in businesses such as Wendy's restaurant, Little Caesar's restaurant, and Amerika Gas Station.

During the case, the prosecution's evidence included cell phone location records that allegedly placed Davis in "close proximity" to these businesses around the time the robberies occurred.

Davis appealed the conviction saying his Fourth Amendment right against unreasonable search and seizure was violated since the government didn't obtain warrants for his mobile location records. And, the 11th US Circuit Court of Appeals agreed with him.

Despite this major decision in regards to privacy and warrantless cell phone location tracking, which was first disclosed by CNET nine years ago, it doesn't do much for Davis. The court still upheld his conviction by allowing the mobile location evidence to continue to be included in the case against him.

Various courts have grappled with the issue of warrants and cell phone location tracking in the past. In 2010, a Philadelphia appeals court ruled that no search warrant is needed for police to track people's cell phone whereabouts but individual judges can "sparingly" require one. While civil liberties groups vehemently opposed this decision, the US Department of Justice said it agreed with it at that time.

(Via GigaOM)