I don't know if Chris genuinely wants to make believe that he's insane though.
He likes to think he's this omnipotent powerful being by using his childish imagination and escapist fantasies. Sure to us he seems like someone who should be thrown in the nut house (and he seriously should be getting thrown in when this is all set and done) but he doesn't think that he has a problem in that regard, he's had this massive disgust about his autism in the past and he doesn't like to dwell on any feelings of hindrance or self doubt.
For that reason alone he wouldn't want to give the judge the impression that he's insane, and even though his lawyer will probably use the angle for the defence that they're unnecessarily "kicking the autistic" with whatever he's charged with, it will definitely irritate Chris big time, and honestly that would be the icing on the cake to see him sperg out at someone who dares to criticise his poor mental state.