Not sure if should put this in spoilers or not but the show is a quite off from the books.
In the books - Graham was the one responsible for putting Hannibal behind bars - though he got disfigured. Now in the show he gets arrested for the murders himself. IMO was a move just so that they could add more suspense points next season.
Thanks for putting up the Spoiler as I haven't read the book stuff .. I much like the pace and the story arc of the show.
From what little I had heard of the show .. I was expecting this guy (Will Graham) to turn into "Hannibal Lecter" .. or that Hannibal Lecter would already be a know Serial Killer like the movies showed and the show was about his FBI hunt ..