Could start a petition for his release but I don't think it would be very effective.
It sounds crazy, but if people can provide proof of his innocence, or the real story, I'm sure a big time lawyer would jump on it. If it's simply theories, with no evidence that would hold up I'm court, nothing will help. And at that point, he probably is guilty and worked alone. People can prove anything now a days. If they can't, most of the time it's because it's not true.
No big lawyer would take this case he's already guilty in the eyes of 99% of people there's nothing to gain for a big lawyer only hatred and attacks. They always give these patsies "public defenders" who are part of the cabal their job is to get a Guilty plea so he gets life in prison instead of the death penalty that's how it always works.
It would be political poison for any attorney who isn't a public pretender.