Not the film you are expecting to see, it's a brilliant alternative universe .
A masterpiece , actually
My only suggestion is that if you weren't around then , and aren't familiar with the case - research it a bit - at least the basics
I saw it with a younger friend , who didn't know much about the case , and when we talked about it afterwards , he understood much better about some of the puzzling comments I made when discussing it
Almost three hours , and it felt like a regular length film.