Character mistake: The new sheriff ("Alice") told Rayburn that she has only been sheriff for a couple months and was still catching up on active cases. Rayburn replied, "Yeah, my daughter's case is far from active." The sheriff then told Rayburn, "My training is very different from the officers around here" - meaning college-educated (Ivy League?), more professional, more effective, and modern. Despite this, some of the sheriff's actions (e.g, walking unannounced into suspects' houses and/or without a proper warrant; questionable "probable cause"; shooting Rayburn to protect her brother) fell far short of the ideal. Perhaps most significantly, the sheriff gave Rayburn a warning shot and told him not to kill Dr. Boone... then she stood back and merely watched Rayburn push Dr. Boone into the pitfall and close the doors while knowing the doctor was severely injured and dying. These things do not show her purported superior training. (00:21:43 - 01:25:34)
Character mistake: Despite it being the writer's creative imagination to have 16-year-old son Tyler kill his serial killer father, Don Burnside, Tyler was reared in what can be considered a highly religious Christian family. Due to his religious, family - and community - oriented upbringing, Tyler undoubtedly was well aware of the Ten Commandments, so suddenly violating at least three (i.e, "Thou shalt not kill", "Honor thy father" and "Though shalt not lie") is too far-fetched. Trusting Kassi also wasn't rational.
Character mistake: When Jesperson imagines himself as a Mountie his uniform is completely wrong and is not even the right colour. As it was his ambition to join the force and he has photos of RCMP officers in his cab, it seems unlikely that he would imagine himself in a completely incorrect uniform.
Character mistake: Although Henry borrowed two books on crime scene investigation from the used book store, he obviously did not learn enough, especially about forensic science. For example, shooting from the tree house could be determined by the location/slant of the bullet in Glenn's head/body, and cutting off tree branches that would obstruct the line of fire could be evidence of pre-meditation. Henry may have thought he planned the perfect murder, but it was far from that. (00:30:30)
Character mistake: Cross knows (for some reason) by memory the last words of the Lindbergh kid kidnapper (and killer) and that Soneji/Mercusio referenced in a book he finds in amazingly oblique ways. He calls him "Richard Bruno Hauptmann", while his name was actually Bruno Richard Hauptmann. (00:42:30)
Character mistake: Zeke makes the bold claim that "John Kramer didn't target cops." This is completely and utterly false, and a cop like him should know better. Kramer repeatedly targeted cops. In fact, both "Saw II" and "Saw IV" have officers (Detective Mathews and SWAT Commander Rigg) as Kramer's main target.
Character mistake: When Jernigan chases the car, he tells the team, "It's heading south on Adams." The toy car then turns left, which means that the car should be heading east. However, Jernigan tells the team that the car is headed west.
Character mistake: At the beginning of the film, Matt arrives at Paddington station in West London. He needs to meet his sister who lives in Chelsea - also in West London. However, for some bizarre reason he gets to her via meeting at Bank station - in east London. It makes no sense why he would make such a convoluted journey. Even if as a tourist he simply doesn't know London well enough to make a more efficient journey, his sister - who lives there - would correct him when arranging a meeting point.
Character mistake: On the way to Jerusalem, Poirot says that "that man, Weizmann, put it rather well the other day, before Lord Peel's commission", and gives a famous quote about the world being divided in 'two places' for the Jews (those where they are not allowed to live, and those they cannot enter). The movie takes place in May 1937, and Chaim Weizmann's quote is from November of the previous year. 6 months are hardly "the other day."