Stupidity: During the final phases of the Turnabout Sisters case, trying to press Redd about him not being solely guilty of wiretapping will cause Edgeworth to state that "unidentified fingerprints several days old were found in the Fey and Co. Law Offices" and they'd "obviously" belong to Redd. That's an unnecessarily ridiculous non sequitur; being an office with several clients, it'd be astonishing if there were no "unidentified prints" at all.
Character mistake: During the tutorial, Phoenix needs to be reminded a few things. The judge asks him the victim's name, and Mia Fey next to him tells him where to look to get that information. Her line though is flubbed, since instead of "the victim's name" she says "Look, the defendant's name is in the Court Record." This mistake was spotted and fixed in the "Ace Attorney Trilogy" remake.