Well you want audience participation then you should definitely make a statement before you choose players, something like "to enter you should be confident in your acting skills, and be able to play a character well" and then maybe the contestants you choose could be placed into a scenario with fake aliases,
like for example, you create 5 or so fake characters in the dangan ronpa universe (oc's if you will) then the players can pretend to be them and be a part of the class trial??? i really don't know, there doesn't seem to be a good way to do audience participation in any way other than letting them find out who the murderer is themselves and then convince it the other players. Though if that were the case then you'd need to make up like 10+ scenarios because audience members might spoil stuff if they played before, and people wouldn't take it seriously, and ugh. Man you sure chose a hard idea for a panel.