William Earl Amanda Knox, an American exchange student who spent nearly four years in Italian prison for the 2007 murder of her roommate Meredith Kercher before being acquitted in 2015, was the inspiration for the just-released “Stillwater,” starring Matt Damon and directed and co-written by Tom McCarthy.Although “Stillwater” spins a fictitious story, McCarthy has not been shy about name-checking Knox during the press cycle, and a Vanity Fair interview with her name in the headline inspired