When Clyde was assaulted back in 1999 he was stabbed in his stomach. Later, when the police capture him, he is not wearing a shirt but there's no sign of a scar in his abdomen.
After Clyde's murder of his cell mate with the steak bone, the blood splatter on the back wall increases from the time he lies in his bunk to when the warden looks into the cell.
When Clyde is making his order for the catered lunch, he orders a "20oz Porterhouse 'Medium', maybe a little bit charred". When the food is delivered to his cell, the waiter calls out each food and when referring to the Porterhouse, he says "Medium Rare", Clyde clearly hears this and does not object. The difference between the 2 temperatures, to an obvious meat connoisseur, would not be acceptable. Additionally, the lunch delivered is not exactly as he ordered: there is no butter squash or pommes frites.
When Nick Rice is flying in a helicopter to rescue Bill Reynolds the helicopter has a "N94PD" call sign on the side of it and the pilot calls out on the radio "N94PD" but when the copter lands it has a "N95PD" call sign on its side.
When the car gets hit by the rocket in the cemetery, the whole car gets catapulted into the air. In the following scene, the car is split in two.
The instant the neurotoxin hit Darby's system he would have fallen down due to being paralyzed. He would not have been able to just stand there, motionless, as muscles are still used when standing still. He also would not be shaking while lying on the table, even when Clyde injected the adrenaline.
At the cemetery where the armed robot emits an EMP, it knocks out the convoy's electronics, yet moments later Detective Dunnigan's radio can be heard. The blast would also have disabled their radios.
During a lethal injection scene three plungers are seen being pressed by a machine to inject the drugs, each in under one second. The largest peripheral venous catheters available have a maximum flow of about 350 ml per minute. The displayed amount of liquids could never have been administered in that short time.
Throughout the film Clyde is being held in a maximum security prison complete with solitary confinement, convicted inmates, and a warden. Pre-trial, suspects are held in a county jail, not a prison.
Clyde is arraigned in front of the same Court of Common Pleas judge who sentenced Darby. Clyde's initial arraignment and bail hearing would not take place in the Court of Common Pleas. In Pennsylvania, it would actually take place in front of a local District Justice (magistrate), who would then schedule a preliminary hearing to determine if enough evidence existed to hold the case for trial in the Court of Common Pleas. Furthermore, this would all have taken place before he was ever committed to county jail.
When Darby is running across the roofs, the path which he is taking is already shoveled. However, this could all have been set up in advance by Clyde, whom we know to be a brilliant tactician.
Even though a cellist would never touch the hair of the bow, Denise is only a student still learning, hence she may have simply forgotten.
When Nick Rice is on his Mac, the software he is shown using is Windows Vista, not OS X. All modern Macs can dual-boot and run Windows natively, so Rice's Mac running Vista is not an error.
The camera in the interrogation room/cage does not have a cable in it. However, the camera could very well be broadcasting a wireless signal, as any loose cable could be cut/unplugged to break the signal, or used as a weapon in the possession of a prisoner.
As Clyde gives Nick and his legal team until 6:00 to release him the camera shows the clock turning to 6:00 for dramatic effect. Then seconds later when nothing has happened yet Sarah's watch is set five minutes fast. However, Sarah may have difficulty with punctuality and, as some similar others do, set her watch a little fast to arrive on time for appointments..
When you first see Darby on the table about to be tortured, Clyde moves around the end of the table. As he does he brushes up against Darby's foot and you can see the foot and end of the leg wobble, revealing that is is made of rubber.
When Darby is running to the cop car, about 20 minutes into the movie, you can see exhaust from the Police Interceptor coming from the tail pipes, but when he tells the "cop" to start the car, he turns the ignition to start the motor.
Over the phone, Kelly Rice tells Nick about the person in the video, "His face was covered." Immediately after the call, Nick explains, "He was wearing a mask." The audience knew the covering was a mask, but Nick had no knowledge that the covering wasn't a dark window or a mesh.
When Clyde tosses the keys back into the trunk of the car that he borrowed from an officer, he touches the trunk edge with his bare fingers, which should've been caught by any investigation into an officer's kidnapping and leading them to him sooner than later as a suspect.
The CCTV camera (an old CTC-5000) shown observing Clyde in the prison interview 'bird cage' has no cable connected the only video output socket.
In a later scene of the same place, the same type of camera shows a red LED stuck to the side of the camera in a small black box facing forward. That camera's power LED is mounted on the rear panel.
Assuming the movie takes place in 2009, the seventh-generation Honda Accord (introduced in 2003) seen behind Clyde as Clyde watches Nick shaking Darby's hand during the press conference in 1999 would not have existed.
The CCTV cameras used for monitoring the prison interview 'bird cage' are IKEGAMI ITC CTC-5000 models dating from the late 60's through the the early 70's. Yet clearly the movie is set in the 21st century. Cameras are replaced at least every decade or so, at the very most.
In the recital scenes, it is obvious that the cello shown on screen is not making the music being heard. At the first recital the bowing does not match, and at the second the finger placement is wrong.
When Clyde is eating the asparagus in his jail cell, the crunching sounds are abnormally loud, do not exactly match his biting motions, and are obviously Foley'ed in.
During the first court room scene a smoke machine can be seen in the background.
The death penalty scene appears to take place at the Philadelphia prison. However, in the state of PA, all executions take place at Rockview. That prison is located in Central PA, approximately 4 hours west of Philadelphia.
One scene shows a car with Nick going north on I-95 over the Girard Point Bridge, but he was previously in Center City, which is well north of that point on the highway.
When the prison guards were scanning and checking Clyde's food, they would've noticed the bone inside the steak and would have had to remove it because it can be considered a weapon.
It is never explained how Clyde could place a huge piece of military ordnance, the robot gun, in a public cemetery and have it go completely unnoticed in broad daylight until it begins firing.
A man of Shelton's caliber would not have opened his front door without first checking to see who rang the doorbell.
At the beginning of the movie, Clyde steals a police officer's uniform in order to trick Clarence Darby (as evidenced by the lack of clothes on the actual officer when Clyde tosses him the keys). This turned out to be unnecessary as later in the film, it turns out Clyde owned several police uniforms in his hideout by the prison. There was no need to steal one.
Clyde states that Darby will only do five years for third-degree murder, he's technically accurate: that is the minimum sentence for a defendant with absolutely no criminal history. However, Darby already has at least one previous felony, as revealed during the phone call to Darby helping him escape. Under Pennsylvania law, a single felony in the defendant's criminal history would raise that to a 7 1/2 year minimum. Assuming that the judge gave them the 7.5-15-year minimum, that would only make them eligible for parole after 7.5 years, no guarantee that they'd be released. Additionally, the judge has the authority to exceed those, and is not bound by any plea agreement.
When Nick and Clyde are in court before the judge, Nick repeatedly refers to his government as "The State". Pennsylvania is a Commonwealth and is referred to as such in court.
Detective Dunnigan explains to Nick that the armed robot used API rounds (armor piercing incendiary) ammunition and explains they're anti-tank rounds. Despite being a somewhat accurate description, .50 caliber API ammunition would be unable to pierce modern-day tank armor.