Two years after his wife's death, Dr. Kirk Turner sat in a North Carolina courtroom, watching prosecutors lay out their murder case against him. He does admit killing his wife, but claims it was self defense. While Kirk is adamant that it was self defense, investigators and prosecutors say the evidence showed otherwise. They believe that Kirk planned to kill his wife that day, and that he even went so far as to cover it up by stabbing himself with the spear. But what would a jury think? Was Kirk Turner protecting himself, or was his wife's death premeditated? Correspondent Peter Van Sant reports on "48 Hours Mystery: "A Killer Defense".