Richard Sutton is a domestic abuser of his elderly girlfriends and the original suspect in the rape and murder of Donna Brooks. It was revealed he didn't kill her and he went into cardiac arrest from the stress of seeing her dead.
When he recovered enough, he defended himself by writing on a white board despite his conscious intubation. The real killer was revealed to be Emma Spevak, the nurse caring for her who hated Donna, as she reminded Emma of her mother Margaret, another one of her victims. (SVU: "Bound")