Revealing mistake: At Mrs. (Louise) Bundy's house, Ressler and McChesney were seated at the coffee table, maybe 3' apart. When Louise was sitting in the chair talking to them, only some hair to represent McChesney was on the left side of the screen and Ressler was not visible. It was obvious Louise was delivering her lines without the two sitting there because her head and eyes were turned way too far to the left and right (beyond where their bodies would have been) to be making eye contact with them. (00:45:25 - 00:46:34)
Continuity mistake: The door had multiple small rectangular glass panes enclosed in wood frames, but the glass pane that Alan Schaefer's head/body went through was larger and no wood frames were visible. (00:40:28)
Factual error: One of the sisters threw a bucket of water over the dock to wash away the blood. Seconds later, the dock was dry. Even with the sun shining, wood does not dry that fast. (00:10:03)
Other mistake: William Tillich (AKA Bill Tell) had one suitcase which could not possibly hold enough sheets (or thin blankets) to cover/wrap all the furniture in his motel room like he did. (His suitcase was not very large and also contained his clothes.) He covered an even larger area of furniture in Gordo's house. It isn't clear if he used his own sheets or just happened to find the same kind in Gordo's house.
Revealing mistake: DEA Agent Rick Bowden was already seated "in the best position" before knowing where Ross would sit in the SF library. Chris Tarbell already had a surveillance camera behind the seat Ross chose, giving him a clear view of Ross, also before knowing where Ross was going to sit. Even if there were cameras in other positions, the DEA Agent and Chris Tarbell being at the right spots in advance was too coincidental to be by chance alone. (00:02:09 - 00:02:30)
Deliberate mistake: The view looking out the windshield showed the man on the bicycle had stopped when he was in front of the car's passenger side, but the outside view showed the man still coming to a stop and then tilting his bicycle. (00:07:12)
Revealing mistake: The blemish/mole that was on the right side of Ghost's nose showed up on her left side (and she was not looking into a mirror). (00:57:40)
Factual error: Unless left in the vehicle (not the case here), towed impounded vehicles do not have keys. Moreover, lacking keys, a valid registration, possibly proof of insurance, and new plates, vehicles bought at a NYPD auction are to be TOWED away. A newly-purchased auctioned vehicle, such as the Navigator in the movie, is "ticket-" or "citation-ready", not ready to be driven on the streets.
Continuity mistake: When Hagmaier is in the Florida State Prison room waiting for Bundy, his hair changes. Initially, his short bangs are straight across the middle of his forehead. When Bundy sits down, Hagmaier's bangs and top of head are "fluffier" (perhaps blown dry) and combed to the side. (00:11:05)
Continuity mistake: Helen's slipper is at about a 45° angle toward the right of the screen when Miss Willoughby finds it. When Detective Jimmy shines his flashlight on the slipper, it is facing the opposite direction. The second time Jimmy shines the flashlight, the slipper is at a steeper angle. (01:00:33)