I have scorn, derision, and condemnation for people who lie and deceive in general. To cover up the murder (intentional or otherwise) of an innocent 6 year old just compounds that.
That said, I think it's... redeeming? (for lack of a better word)... of them, at least to me, that they came together to protect and cover for their remaining child. Honestly, that is what seals the BDI case for me. He is the only thing I can imagine both parents coming together to protect. I really don't believe either would cover for the other for so long, but I do believe they'd want to protect him.
I can't imagine anything more heinous than the murder of a child and the denial of justice to her. We'll continue to disagree that they covered to protect their other child. I think they blamed their other child in order to protect themselves.
JMO