They suggested he killed her to be free because a baby was on the way, any day. No one saw him kill her, there was no cause of death because the body was eaten and mutiliated by fish and bloat. Lacy was at least old enough to drive away by herself or answer a door to a stranger bent on harming her - Caylee wasn’t. Caylee was with her mother, and it was testified to by George that he saw her drive away with Casey. At least Scott had the sense to pretend to be sad for a day or two after his wife disappeared.
Scott tried to flee the country with 10K. He was toast.