Arguing before the Supreme Court, American Civil Liberties Union lawyer Nathan Freed Wessler said a warrant would provide protection against unjustified government snooping.
Supreme Court frets over erosion of privacy in digital age →
In Carpenter's case, authorities obtained cellphone records for 127 days and could determine when he slept at home and where he attended church on Sunday, said the ACLU's Nathan Freed Wessler.
Supreme Court ponders need for warrant for cellphone tower data →
