This is one of the most fascinating and frustrating aspects of this case. The parents know more, but they've remained tight-lipped from the beginning. As I mentioned on another thread, I understand they're trying to protect their son, but they're doing more harm than good. If their son committed this crime, he must be held accountable. Lawnmower parents can't stop it.
It looks to me like the end of the road for Brian is death or a lengthy prison sentence. His parents might be in denial that those are the only options, or they might think they can delay it. Of course, the autopsy results will have an impact on the available options.
If he ends up dead, they only have themselves to blame.