So, it appears that their " swinging lifestyle" was not so secret " behind locked garage doors" to keep from their children. It's difficult to believe these children were NOT exposed to their parents deviate sexual behavior.
I think these children saw MUCH more than young minds should. Sad, very sad. Sad because their parents allowed perverts and immoral "friends" into their home and God only knows if this led to the awful tragedy of their daughter.
If you're suggesting that the little girl was killed because her parents smoked pot, drank beer, and engaged is the swinging lifestyle, then your logic is seriously flawed. From everything I've read, Andrea Yates didn't smoke pot, drink beer, or swing, and God was a very big part of her lifestyle, yet she murdered her own children. If I follow your logic, then one could argue that abstainance and God caused Yates to kill her kids.
BTW, I smoked two hits of pot last night and drank a pint of Harp around midnight -- about two hours after my kids went to sleep. I also had wild sex with a woman who is not my wife. And guess what? Both my kids woke up smiling in their respective beds this morning.