A federal appeals court is being asked to decide if the government must obtain a warrant before placing a GPS tracker on a suspect's car.

The case before the 3rd U.S. Circuit Court of Appeals in Philadelphia involves three brothers suspected of robbing pharmacies. A led to their arrests in 2010.

Lawyers representing the trio told a three-judge panel Tuesday that warrantless tracking violates the Constitutional guarantee against unreasonable searches.

But a contends that authorities followed relevant legal precedents in attaching the tracker without a warrant. He says authorities had probable cause to suspect illegal activity.

A lower court previously ruled in favor of the brothers. The Justice Department appealed based on a recent Supreme Court ruling. It's unclear when the appeals court will rule.