Just think about Hitler trial.
Saddam trial (if he ever had one) might be a good starting point...
Saddam did have a trial, but the problem is that one was a bench trial (because he was tried under Iraqi law, which uses the Napoleonic system), and that several officers of the court had conflicts of interest which would not fly in an American courtroom.
If OBL sees an American courtroom (which isn't that unlikely, it makes for good propaganda for American Democracy, after all), expect there to be no live coverage from inside the courtroom (there will be of course drawings of the proceedings as well as transcripts). The venue will probably be in the Southern District of New York or the Eastern District of Virginia. Voir dire will be a bitch, it'll be like the Shkreli trial on steroids, but it will get done.
If OBL can't get a private attorney, then he probably ends up like Tsarnaev, who got a public defender. In any case, any criminal lawyer, prosecution or defense, gets it hammered into them in law school that a defense attorney's job is to make sure that, if the defendant gets convicted, the government proves every element of every charge beyond a reasonable doubt. It's not really necessarily "did Osama do this?" It's "Does the prosecution have their ducks in a row, can they prove every element beyond a reasonable doubt?" So defense counsel will probably go over the prosecution's evidence with a fine toothed comb, looking for any consistencies, any bias on the part of witnesses.
Because of the nature of the case, the trial would probably take years, though, even without counting appeals.