This undated photo provided by California Department of Motor Vehicles via The San Diego Union-Tribune shows Shirley McGill. Robert McGill was being held in the death of his wife, Shirley McGill, aboard the Carnival Elation. She was killed during a five-day trip to Cabo San Lucas, said Keith Slotter, special agent in charge of the FBI's San Diego bureau. (AP Photo/California Department of Motor Vehicles via The San Diego Union-Tribune)