Stupidity: For a brilliant criminal mastermind, Cyrus makes so many idiotic mistakes. (1) He leaves his entire escape plan hidden in the wall for the guards to find later instead of trying to dispose or destroy them (2) He makes the fatal mistake of trusting Santiago completely and never suspecting a double-cross. At the very least, he should have checked all of Lerner airfield just in case the plane was hiding (which it was). (3) He never notices or even questions Billy Bedlam's sudden absence until he sees his body. Odd considering he notice Santiago's absence immediately. And (4) When escaping on the firetruck, he (pointlessly) chooses to ride on the ladder instead of the front seat where he stands out, and Poe and Larkin both spot him. No surprise his whole plan failed.
Stupidity: The bodyguard takes Michael's pistol from him and later shoots the pistol near Michael's ear, deafening him, then beats him a bit and leaves him on the ground. As the bodyguard is walking away he gives Michael his sidearm back by ejecting the magazine and tossing the gun on Michael's body. He however didn't eject the bullet in the chamber. Michael's gun, a Sig Sauer, doesn't have a magazine disconnect which prevents a gun from firing with a magazine removed. This was a safety feature for police. (01:33:00 - 01:37:00)
Stupidity: The whole premise of the plan is summarized by Helen in the sentence "They don't know Andi is dead, so why would they suspect anything?" However, "they" conspired in unison to financially ruin her sister, and "they" did not answer the mail, none of them. The possibility that "they" all could have gathered and silenced her by force is one of the most likely ones, and yet neither she or Blanc consider even for a moment that the literal crime conspirators could have conspired.
Stupidity: Robocop is just about to be unveiled to the press for the first time, and they decide right beforehand is the perfect time to upload a massive amount of data, including his own attempted murder. Then, they seem shocked when that causes problems. No reason to do that right before a very public, time-sensitive moment except for the sake of the plot.
Stupidity: When an explosion hits the courtroom, Arthur is the closest person to it, with nothing to protect him, but he is the first and only one to recover, and every bailiff (not to mention the police outside the courthouse) outside of explosion range is mysteriously knocked out and/or absent.
Stupidity: The 1st time Foley enters the warehouse with the woman, 2 guys enter with the wooden box and black bags on top to transfer the bonds, then take it back to the truck. Why enter the warehouse at all when they could've put the bonds in the bag anyway, inside the van? They had no reason to go to the warehouse at all. (00:42:20 - 00:43:25)
Stupidity: When Stuntman Mike is taking photos of the girls, he is shooting with the lens cap on the camera.
Stupidity: (SPOILERS) Despite knowing that Rowena killed the last person who was blackmailing her, Miles tries to use her secret to blackmail her into sleeping with him. Did he really believe that she wouldn't react with such drastic measures like she did before?
Stupidity: Jack has been using Mosley's badge and identification to pass himself off as FBI. He never once uses this trick to commandeer a civilian car for him and John when it would have been the safest way to get to L.A. much sooner.
Suggested correction: Probably because If he did that, the car's owner like Red the bar owner would eventually call the FBI office to get their car back and then the feds would know the make, model, license plate, and the last location of Walsh and the Duke. The police would have caught them in minutes. Walsh had to keep a low profile.
Stupidity: Vincent's choice to cut the power to the building that Annie is in does nothing but waste enough time for Max to save Annie. It would have been easier just to go up to kill her and he probably would have gotten away from the police if he did so.
Suggested correction: It also slows Annie and Max down by forcing them to walk in the dark, and also, at this point, Vincent is really torn up from the crash, and the mere sight of him is going to make Annie very suspicious or even afraid, unless the power out (which for all she knows is just from the building) gives him a plausible reason for being so mauled.
Stupidity: After one of the policemen decides to jump over the railing and right into the angry mob (!), Arthur just easily sneaks by ducking under it and takes a nice stroll that will lead him through an unlocked door. Nobody in the mob he is part of decides to do the same, and you can also see that one of the policemen is turned towards him, but does not even yell at him or move. And of course, with the theater packed with the Gotham elite basically under siege by a mob and guarded by the police, the door is unlocked and unchecked. Why not. (01:02:55)
Suggested correction: The point is they were all too distracted by the tussle to notice Arthur ducking behind the barrier. No cop sees him. The angry mob is controlled by the barrier and not all that large so they haven't taken extra precautions to keep the mob at bay, yet. The door Arthur gets in is probably a fire escape and can't be locked for safety reasons.
I think that with an angry mob worth putting barriers and a big police dispatch, they'd tend to lock the door that is like a 20 feet of walk in a straight line. I mean, they have barriers in front of the stairs, but at the base of the stairs there's an unguarded, unprotected, unlocked door. It's just funny. Not even something in the back or around the corner, no; literally one step to the right of the blockade.
Stupidity: The fact that Nolte even gives in to Eddie's demands is ridiculous. Why not just interview him in prison, ask him where to look for certain people, etc, and if it's a dead end, report back and ask for further tips, etc. They had zero problem going to prison and asking Kirkland Smith in the sequel.
Suggested correction: He refused to tell him anything unless Kates takes him out of prison.
Stupidity: It is pretty silly for Martin Lawrence to go undercover as a police officer when it would make way more sense to go undercover as a janitor/custodian since his main goal is to gain access to the vent. A janitor would be a way less conspicuous disguise than a detective and slipping through a backdoor entrance disguised as a janitor should not be all that complicated for someone as savvy as Myles. But of course this would make a far less entertaining film.
Stupidity: When the crew go to New York they are in the back of a fish truck carrying fish. There's no need for them to do that. So long as the truck looks normal outside to keep their cover, they could have the inside kitted out any way they want. When they get to the fish factory they open up the warehouse in front of the workers to reveal the cars, so the workers are in on it being a front - it makes no sense to actually have fish in the back of the truck.
Stupidity: One of the major reveals and plot twists of the movie lies in the fact that a certain character is an accomplice of the medium. The reveal, though, does not explain at all how said individual managed to fool Poirot; the trick briefly shown involves a simple rope pull to open a door. Poirot was looking exactly for that kind of trick, paces around the room constantly on maximum alert, and examines the door itself later. Likewise, it does not explain where and how they could hide the stuffed animal.
Stupidity: There is a scene about a null hypothesis proving Cassius is the killer. Nearly everything is wrong in this scene. Statistically, you never prove a null hypothesis true. (01:23:11 - 01:24:22)
Stupidity: When she leaves him at home with a sandwich she says people will come check on him. When she gets home and he's not there, she doesn't go and ask those people where he is.
Stupidity: The metro police officer (and co-conspirator) went to the old cement factory where the other bank robbers were. Since the police officer (accomplice) wanted the money and did not want other police officers to be nearby, he called 911 and made an anonymous false report stating he spotted the person police were looking for and misdirected them further away. Maybe a good idea, but he made this call using his own cell phone. (01:12:20)