Character mistake: When Dana Appleton objects to Fletcher badgering Kenneth Falk, the judge overrules because Falk is Fletcher's witness. You still aren't allowed to badger your own witness in a trial, which the judge should certainly know.
Character mistake: When John Henry Irons is arrested, two police officers lay him face-down in order to zip-tie his wrists behind his back. A close-up of Irons' hands, however, reveals that the zip-tie only wraps around his right wrist while crossing about mid-way on his left thumb, meaning that he could easily remove his left hand from the restraint with very little effort. Arresting police officers would never make this mistake in real life.
Character mistake: When Darcy walks into the police station the chief calls her Joan, the lead actress' real name, by mistake.