Stupidity: There is no logical reason for a bookkeeper to be present at the liquor deal on the Canadian border and even less of a reason for him to bring the primary ledger with him. This is compounded by the fact this is merely a secondary bookkeeper and the main bookkeeper is subsequently subpoenaed by the district attorney.
Stupidity: At the start, when the bank robbers pile into the car, Frank flips a switch and the licence plate changes...out in full view of the public. Given how well-prepared Frank is demonstrated to be, that's absolutely something he would have done in private, before arriving at the bank.
Suggested correction: The plate is changed after the robbery for a reason. By allowing plate A to be seen during the robbery the information will be relayed to the police that a car with registration plate A is involved. Swapping to plate B after the robbery ensures that police will see plate B and know that the car is not involved.
But the point is he drives up to the bank with plate A on display. The robbers pile in and he switches to plate B. So any witnesses have seen both plates (plus the fact that the car switched plates, doubly suspicious). Whereas if he'd switched to plate B while out of view in the car park, he'd still have a "clean" plate to use.
Stupidity: The crack house workers are all topless to prevent 'hiding' any product for personal use. Yet are also wearing parachute type pants that they could easily hide things in.
Stupidity: Andy meets Tommy Williams who names another convict who described the scene of the murder of Andy's wife and her lover in sufficient detail to convince anyone that something was wrong with Andy's conviction. Andy then goes to the Warden, a man he knows to be utterly corrupt, a man who will suffer a huge loss if he is acquitted. Andy is an intelligent man - why would he do something as stupid as that? Why doesn't he write to his lawyer? This is a matter for an appeal court, not the Warden.
Stupidity: The first time they see the bad guy in the Land Rover, Morgan has him in his sights but can't shoot, as he doesn't want to kill him. Clearly, the obvious thing to do is to shoot the car tires, but he doesn't and lets him drive off.
Suggested correction: Shooting out car tires is not an actual effective strategy to get a vehicle to stop. A 9mm bullet simply doesn't cause enough damage to a tire to get it to go flat immediately. It causes similar damage as running over a nail. It is a movie cliche, similar to using a gun to shoot out a lock or a rope, it just doesn't happen in real life.
Stupidity: When they raid the warehouse as the criminals are trying to leave town, they load the girls into.a white van. A man (Bruce Willis) wearing a ski mask gets out of the passenger side and covers with his pistol as they load the girls into the van. The entire time the slide on his weapon is back, so the gun is not ready to fire.
Stupidity: At the end Vince fires a grappling hook at the passenger seat of the truck then attaches the other end to himself, all the truck driver has to do now is hit the brakes and Vince would be dead under the truck or dragged along the road.
Suggested correction: In point of fact, the truck driver does slam on his brakes; but, defying physics, Vince is catapulted around the right side of the truck to the passenger door.
Stupidity: After Jack is found not guilty, you would think the first thing he would do is to get rid of the typewriter he used to send the notes to Teddy to manipulate her into winning the case for him, especially when she is sleeping with him at his home. Not to even mention the fact he hid the typewriter in an unsecure manner in a closet behind a stack of towels, a place where it would very easily be found. This foolish mistake exposed the truth to Teddy and cost him his "freedom."
Stupidity: After Roy escaped from the factory, he encountered a metal garage-door-type gate that was open at the bottom to the height of his knees. Trying to sneak away and in obvious pain from his injuries, it would have been quicker, quieter, and probably less painful if he crawled through the opening. Instead, Roy pulled downward on the chains, making a lot of noise, and it didn't even get the gate halfway up before he bent over to get out. The gate went up more after he stopped pulling on the chain. (01:15:29)
Stupidity: When the police turn up the first time the mother lies to them to get them to go away but the burglars can't hear the conversation. She could have told them exactly what was happening and that she had to make it look like she'd got rid of them. She could have then smashed all the cameras and just let them in.
Suggested correction: This was a character decision, and a completely understandable one. Her daughter was being held hostage in the panic room. She decided to cooperate with their demands for the safety of her daughter. Your idea is a solid one, but she simply did not think of it in her state of mind. She opted to get rid of the police, and her decision is not a movie mistake.
Stupidity: When Steve Martin reaches the beach with the wheelchair, he tips it over, giving the illusion that he fell out of it. However, with where he starts crawling on the beach, it's tipped the wrong way. If it was that way, he would've been on the other side of it. A clever con-artist should know better.
Stupidity: The protagonist has a sophisticated alarm system with cameras...that do not properly show who is at the gates (the cameras are positioned in a way that does not show the face of the person ringing). The bad guys are disguised as police officers...and wear ski masks, which would have made the disguise entirely pointless - but luckily for them, Nicholas Cage can't operate cameras nor looked at the ones on the entryway or the front of the house, didn't open the door sooner nor peeps before opening. They could not know any of that, though, just that the camera at the entrance has a terrible angle.
Stupidity: Joe's second homicide aims to be ruled as accidental death, but Joe's plan involves a furious struggle with the guy underwater, who claws and bites at his arm, as he applies pressure to his shoulder and neck. Moreover, their struggle happens close to the water surface but the bodyguard who is there does not hear or see anything. (00:35:00)
Stupidity: Jimmy parked his truck on the side of the road with woods running parallel and starting about 10' away. Jimmy moved to the passenger side so the Sheriff could sit in the driver's seat (for no apparent reason). After Jimmy threw the "white powder" into the Sheriff's face, he quickly got out of the truck and ran straight ahead on the road instead of ducking into the nearby woods. The Sheriff had a clear and easy shot to hit and kill Jimmy. Also, Jimmy should have been much further away. (00:11:51 - 00:12:21)
Stupidity: Ilona Bergen's murder happening as shown is laughable; she sees the hand with the syringe coming, slowly, at her, and not only she can't defend herself or avoid it (because, damsels in distress in the 60s, you know), but she does not even scream. There's no way the killer could have been sure, or even take a calculated risk, to murder her in such a way. (00:55:25)