A federal court case in Pittsburgh could reach the U.S. Supreme Court for a "groundbreaking" decision about whether police officers need probable cause and search warrants to use GPS technology when tracking suspects, a local expert in constitutional law said. Across the country, detectives are using the sometimes-controversial technology to investigate cases. But Pennsylvania law doesn't clearly dictate rules, said University of Pittsburgh School of Law professor John Burkoff, author of the "Search Warrant Law Deskbook." "The law isn't entirely clear," Burkoff said. "There are many areas open to challenge, and to be safe, the best bet would be for...