I can't remember what video it was in, but before they confronted CW, Agent Tammy asks CW if they find SW and the girls murdered, what does he think should happen to the person who did it.
And he gives a cold, clinical, non-emotional answer that then they should get the death penalty or if Colorado doesn't really do that, then life in prison. But no emotion or anger like how he would want them dead or suffer or what he would want to do to the person who did this to his family.
Which of course he didn't have that emotion because he is the guilty one! But even more was telling that if he was going to blame this on SW, he should have been all, "I would want to do to them the exact thing they did to my daughters, those were my kids."
My favorite part of the polygraph video is when awesome Tammy says, "Wow, the good news is, you are a horrible liar! Has anyone ever told you that? That was awesome. If you lie it will be really easy to tell!"