I think that such a gamemode can function with friends.
Look at L4D2, a game Badspot and Rotondo both like. You can go into any expert server and unload your shotgun into all of your teammates, incapacitating them instantly with one shot.
There is retroactive votekicking, but that doesn't keep people autonomously from violating game rules.
Jail RPG is pretty stuffty, though, in all walks of life. You already know who the people you're going to be killing are, you're just waiting for "evidence."