Is it possible that Zimbardo is now legally responsible? He influenced policy in this way, with what seems to be obvious malicious intent, and he also apparently testified in many court cases. Can he be prosecuted for this?
Actually he probably thought he was doing a good thing. He didn't intend to harm people, but to help people (by creating a fraudulent narrative that would work towards the greater goal of prison reform), with enough fame and personal profit to sweeten the deal. It seems likely to me that Zimbardo believes the ends justify the means.
Still, it would be satisfying to see him prosecuted for this fraud.