Ocean, this touches on a whole 'nother topic: Why do so many family members believe in innocence? I'm not at all sure that they actually do, but I've come to think it's just familial loyalty over justice. I saw a case, "up close and personal", where a woman killed her husband (actually, two), then when she came under suspicion, framed her daughter for the murder and attempted to kill her as well. I never understood why the grandparents of the young woman framed by her mother stood by the mother and proclaimed her innocence. It was so obvious who the culprit was!
I mulled this for so long, since one reason could have been that blaming it on the granddaughter was safe -there was no way she'd ever be convicted of the murder. However, I ultimately decided that what was really going on was the "blood is thicker than water" concept: The daughter was closer in blood/bond to the grandparents, and they were willing to let their granddaughter be blamed for murder, so as to save the murderous daughter. Awful.
Thankfully for all parties involved, the mother was convicted and died not long after in prison. It is thought she not only killed two husbands, framed her daughter for murder and attempted to murder her, but that she also murdered her own father.
So, "state of denial", I'm not so sure. Maybe in some cases, but I think in many it's just saving one's own, no matter the travesty of justice.