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.
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)
Factual error: After Ressler tells McChesney he wouldn't be surprised if one day she's tracking down sequence killers, McChesney replies, "Not sequence killers. Serial killers. That's what they should be called." But it was Ressler who claimed he coined and is often credited with coining the term "serial killers" (at least in the U.S). ** After showing pictures of some of Bundy's victims, Ressler is shown and it is pointed out, "He [Ressler] is credited with coining the term 'serial killer'." (1:31:30). (00:26:40)
Other mistake: Blood gushed out of the bound man's lower inner arms that were slit with a knife from below the elbow to the wrist (then turned toward the ground). A switch to an aerial view showed no additional blood dripping (while he was still alive). Also, blood would not pour out of his arms to the ground in a horizontal stream like it did. (00:02:04 - 00:02:27)
Other mistake: The issued sidearm for the Spanish National Police is the H&K USP 9mm Compact, which has a capacity of 13+1 bullets, and the Civil Guards' is the Beretta 92fs/M9, which is a 9mm and has a magazine capacity of 15+1 bullets. As of 2020 the Beretta is being phased out for the H&K USP C. The police officer fires a total of 5 bullets from his Beretta then the slide locks back because its dry. He has no magazines for reloads either. I highly doubt the Spanish police issues 5 bullets to their officers. (00:33:00 - 00:35:30)
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)
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)
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)
Revealing mistake: During one of the chase scenes, an SUV hits a rock barrier and flips over landing on its top. The car spins around, and we see that it is empty. The driver then climbs out as if he was just in the vehicle.