I agree. You can never trust a human being, even the ones that are closest to you that you think you know the best. Every serial killer show I've watched has a relative or friend on it who says something like, "I was married to him for 20 years and I had no idea what he was doing when he went out," or "I'd been friends with the guy since kindergarten and he was the nicest guy!" Or similarly, speaking about the victims of these people, their friends and family say that everyone loved them and they didn't have an enemy in the world. Then they come to find out they had a drug habit or something and got killed by the dealer they owed money to. Just goes to show that you never really know anyone fully, 100%. Thusly, no one can be fully trusted imho.