The U.S. Supreme Court will hear oral arguments sometime in its coming term in one of the most significant Fourth Amendment cases in years.
At issue in Carpenter v. United States is the question of whether the FBI violated the Fourth Amendment when it obtained, without a search warrant, the cellphone records of suspected armed robber Timothy Carpenter. With those records, federal officials identified the cell towers that handled the suspect's calls and then proceeded to trace back his whereabouts during the time periods in which his alleged crimes were committed. That information was later used against Carpenter in court.
http://reason.com/blog/2017/09/01/in-warrantless-cellphone-search-case-its