I think the defense will try to plant doubt that the driver of the car seen on video was actually CR. Maybe it was someone else who has access to that car. Maybe CR confessed to protect someone else and his "blocking out" really means that he doesn't know the details of how she died because he wasn't there. Or maybe CR was present at the time, but wasn't the one who actually killed her. If DNA shows a SA by him, he can say he assaulted her, but didn't stab her but someone else did. He wouldn't necessarily have to name that other person - all they need to do is plant reasonable doubt.
I think there is room for a defense to be built. Whether it's true and/or believable is up to the jury.
FWIW, I think he's the perp from what we know, so please don't take this post as a defense of him. I'm pointing out possible ideas the lawyer might use. I am placing hope on lots and lots of DNA and other physical evidence that proves beyond reasonable doubt this is the perp.
JMOpinion.
CR admitted he was driving the car and he removed her body from the trunk. He admitted he became enraged. That is enough to convict him whether he had a co-conspirator or not. We'll know that if there is other DNA on her