Atom Egoyan has no sense of pacing. The movie just drags. His biggest mistake is he completely misses a chance to bring the locale to life, like Richard Linklater did in Bernie with a more documentary-esque style. Which leads me to strike 2:
A documentary would better serve this subject matter - and it has. There are SEVERAL good documentaries about the Memphis Three.
Strike 3: Nobody wants to see Colin Firth do a Southern accent.