Here's an issue with the forum game format I wouldn't have if it was a suggestion game (and I don't want to do this as a suggestion game if it ever happens):
In the video games, there are four parties. In forum games, there are often two (GM and players)
Defense: Obviously player-controlled. You defend witnesses by proving their innocence in courtroom shenanigans. This doesn't present a problem. Players would have the same capabilities as Wright himself: access to character profiles/evidence, pressing/objecting, and the Mistake Meter (or whatever you call it - how many mistakes you can make before losing entirely).
Judge: The Judge is a completely neutral part and the final arbiter of courtroom decisions. I considered both GM control and suggestion control, but a mixture might be interesting: the GM would act when the trial is "won" or "lost" and remind players of the rules, but there could be suggestion-style votes for prodding either party (prosecutor or defense) like the Judge often does in the game.
Prosecution: The prosecutors in Ace Attorney are out for blood (exemplified by Miles Edgeworth, the most iconic PW:AA prosecutor). They do not present testimonies but rather try to distract the judge and the player from the obvious truth. Handing this over to the players or masses would make it, essentially, a PVP game, and that creates a whole mess of issues (both sides would need to know and believe different things, for example). By default, I'm going to say the GM controls the prosecutor.
Witness: The only party that MUST be GM-controlled (because the player actively fights them - verbally, at least). I would have to write every detail and subtlety of witness testimonies beforehand.
In essence, GM and player are spread over the four parties in different ways.