A federal appeals court in Philadelphia is expected to hear arguments tomorrow in a case challenging the constitutionality of the US government’s use of cell phone records to track the movements of suspects or persons of interest in investigations. Investigators have been able to identify an individual’s movements and locations based on GPS technology in many cell phones or the nearby phone towers used to beam a given call. The Electronic Frontier Foundation and ACLU have filed suit to block the tracking, saying it violates privacy rights.