This isn't a bad theory, to say he's an untrustworthy narrator is an understatement. Plus, we don't know the nature of the evidence they got from Barb. Maybe she denied it all, refuse to be examined for evidence.
If that is the case, it's pretty shocking that they kept Chris in a cage for 18 months. Not saying I feel sorry for him, because he deserved every minute of that for what he did, but the idea they can subject someone to that when they didn't have enough evidence to charge them is insane. It's madness. It's not even like Chris was a potential danger to the public.