Dawson Casting: In a minor example, David Tennant was 42 when the series was released, but Burton is stated to be under 40, though his exact age isn't mentioned.
Playing with Character Type: Tennant as William Burton to an extent, given how his character starts off normally but then turns into a brilliantly savvy murderer; it is, however, worth noting that he has played these sorts of characters before, albeit as far back as eight years ago in the case of Harry Potter.
Shown Their Work: David Tennant actually went to The Old Bailey to observe the procedure in the Crown Court, in order to make his performance sound more believable.
