DETROIT — Federal investigators in Detroit have taken the rare step of obtaining search warrants that give them access to Facebook accounts of suspected criminals. The warrants let investigators view photographs, email addresses, cell phone numbers, lists of friends who might double as partners in crime, and see GPS locations that could help disprove alibis. There have been a few dozen search warrants for Facebook accounts nationwide since May 2009, including three approved recently by a federal magistrate judge in Detroit, according to a Detroit News analysis of publicly available federal court records. The trend raises privacy and evidentiary concerns...