A U.S. district court has begun hearing arguments in a case with major implications for the government’s secret tracking of cell phones. Daniel David Rigmaiden, who faces fraud charges, wants the government to disclose its use of “stingrays,” a device used to track mobile phones even when they are not being used to make a phone call. Rigmaiden’s attorneys say the stingrays have violated constitutional protections against unreasonable search and seizure.