In the first four seasons Mary's grave is surrounded by eight electric lights set flush with the plaque. In this season they're changed to candles to match Hanson's trial testimony.
Hanson had first attacked (killed?) the duty nurse before going into the ward to attack and attempt to murder Jack, a "small" detail that was subsequently overlooked completely! Then, Brian testified that he had hit Hanson with the Oxygen cylinder when actually he had used his crutch and it was Jack who used the Oxygen cylinder to hit Hanson as Hanson was in the act of killing Brian (breaking his neck).
In addition, when Hanson goes into the ward to attack Jack Halford, he'd put on a white coat and had a hospital ID tag, which doesn't square with his story of the reason for the visit.