Dan Garrett is the killer of his finance, Dr. Jenny Gorham. Garrett was having an affair with his counselor, Dr. Diane Meade, and when Jenny read his passages in his journal about the affair and Meade told Garrett to get it back, Garrett choked her to death.
Garrett took a plea for a reduced sentence of four years in prison for manslaughter in exchange for testifying against Meade. Meade received probation after a plea of criminally negligent homicide due to her circumstantially facilitating the murder. (L&O: “Promises to Keep”)