The Darin situation is certainly puzzling in this case.
I can't fathom why he would stay by her side if he was not involved.
On the other hand, the only evidence against him that I am aware of is his weird behavior beginning the night of the murders and continuing to this day, his failed polygraph (inadmissable in court), and the claim that he approached someone about burgling his house for insurance money.
Well, that does seem like a fair amount of evidence, but does anyone know of anything else?
Can anyone post a link to the habeus corpus motion?
The best theory that I can come up with are these:
The parents both arranged to have the boys killed, not just for the insurance money, but also to eliminate both a financial burden and a hindrance to their lifestyle of "grown-up fun".
I don't know whether they thought of this, but I wonder if D & D expected donations from well-wishers to pour in for Drake the way they seem to do for other crime victims, for example, OJ Simpson's children.
It is possible that the arrangements were made for the crime to be committed, and when the hired gun failed to show up as planned, on time, etc, Darlie lost patience and took matters into her own hands.
Or
Perhaps Darin caught her in the act and Darlie threatened that if he told on her, she would say he did it and stabbed her, too. And he probably believed that everyone would believe Darlie over him, and covered for her out of fear.
Of course, that does not really explain his continuing to support her all this time, but who knows?