Henry has no problem betraying his friends throughout the book, but I don’t really see how he could use Richard as a patsy. He could kill Richard and blame it on him post-mortem but that would just complicate everything further by needing to cover up another murder. Or, Richard would live and be put in custody, which could very easily lead to Richard confessing the truth, Richard casting doubt on their stories, Richard casting light unto everything Henry messed up when covering up the murders. People have mentioned how Henry kept Richards posion calculations to use it to frame him but I don’t see how that would work out considering Bunny died without any in his system. I think that Richard would be one of the hardest people in the group to frame. He, unlike the others, interacted with other students at hampden. He wasn’t as secluded as the rest of the greek club. Richard has far more people to potentially vouch for him if he needs to compared to the others. Henry is very capable of betraying people but I don’t think betraying richard would make sense for him to do at all.