When the dart Kruger pulls out of his belt to throw at DeGuerin is airborne, you can see wires, as well as the trajectory being off from where Krugers hand in and how he threw it. Also, when it hits DeGuerin's arm, it doesn't lodge into his arm - you can actually see it deflect via the wires.
After the Lee and Kruger escape from the zoo, deGuerin tells Belly that he lost 3 troopers. However, Kruger releases the Crocodiles to eat deGuerin's 3 troopers. Kruger himself, when he breaks into the Crocodile room, he shoots one deGuerin's trooper. So, deGuerin should say that Kruger killed 4 of his troopers.
When Kruger and DeGuerin are divided between the glass wall, DeGuerin speaks to Kruger through the wall and can be heard easily, but Kruger's loud yell afterward was almost undetectable on the other side.
During the scene where the Cyrez hitmen are attempting to kill Lee in her home, it is shown how the scopes on the railguns can see through multiple layers of the house (and apparently even select which layers to view) yet they can't see through a refrigerator.
Near the end of the movie, Lee and Kruger are looking at the offshore bank accounts. Lee says pointing at the screen, "UBS, that's Union de Banque Suisse." Kruger brings up information about the "UBS" account, except that instead of "UBS" the computer screen now reads "USB" and stays that way through the rest of the scene.
DeGuerin passes round a photograph of the woman. One agent holds the photo, upright, by the bottom edge and passes it to Kruger who takes the photo by the top edge and looks at it. The photo should now be inverted as Kruger looks at it, however the shot from over his shoulder reveals that the pic is still upright
When Kruger opens the door in the plane he switches from holding on to something (to avoid getting sucked out of the plane) and holding the gun with both hands, between shots. (And if it was so important to hold onto something, wouldn't he have been sucked out of the plane when he was holding the gun with both hands?)
During the battle in the reptile house at the NYC Zoo, DeGuerin's men spot Krueger and Lee through wire-reinforced door glass. They then break the glass with their guns and open the door by reaching through the wire-free window remnants.
When Deguerin holds Lee hostage on top of the container and tells Kruger to drop his gun, in the first shot he is seen pointing his gun at Lee, in the next (long) shot he is pointing it at Kruger, and then he instantly points it back at Lee.
When Kruger and Deguerin are fighting on the moving container, in the long shot Lee is seen letting go of the cable and crawling on hands and feet towards the gun. In the next shot she is once again holding on to the cable.
Possibly deliberate: When the EM gun is used in the attack on Lee's (Vanessa Williams) house, it needs to be plugged into a satchel battery to operate. In the climactic battle, none of the EM guns have a battery pack. This may be deliberate to indicate a prototype vs production model, or to show they can hold a limited internal charge.
John alarms the pigeons at the warehouse and before the two thugs beneath him get alarmed too, he jumps on them. He first jumps and while he's mid-air, guys fire at him. But the ricochets start before they fire.
John takes the fridge down, then Lee and him duck behind it to avoid the x-ray scope of EMP Gun (This action's usefulness is even up to a debate anyway, since the scope is successful at penetrating multiple walls and furniture). Before he knocks it down, EMP rounds come from the back; after they duck, the position changes to front immediately.
When John and Lee are leaving her house in the van, a man is firing from behind. Two bullets go through the windshield of the van. However, in the next wide shot scene of the van, the windshield is unharmed.
When at the gay bar, when Kruger is enlisting the help of Johnny C, we see Johnny begin to remove his jacket, when Kruger asks if he and Kevin need a moment alone Johnny Cs jacket reappears. We then see him folding it in the next shot.
When the picture of DeGuerin's witness is being handed round, you can plainly see the person handing the picture to Kruger passes it to him so that when he takes it, it will be upside down to him. The camera quickly cuts to a closer-up shot and now suddenly the picture has rotated so it's now the right way up for Kruger
The nurse responds to Johnny C's "flat-line" asystole rhythm by saying "he's fibrillating." Medical personnel do not shock without checking for a pulse. Nor would they shock someone moving or speaking. This is obviously a clear shot at some medical personnel lacking training or just inserted as a gag for the viewer.
The green circle of light supposedly emitted by the scope also pierces through solid, opaque surfaces as seen in the warehouse scene when a thug picks up Kruger's jammed shotgun and is subsequently misidentified by his partner, who is looking through an x-ray scope because he has no direct line of sight to the target.
The house thermostat depicted is a common design with a mercury switch. Any spark when the heat goes on is confined to the sealed capsule containing the mercury, and hence cannot possibly ignite anything.
After firing several shots at a bulletproof glass door with a semi-automatic handgun, Deguerin turns his gun on Lee and threatens to shoot her. But hammer on his gun is down when it should be fully cocked from the previous shot.
The technician on the 727 is able to trace John Kruger's call from his cellphone, to an apartment in NYC. However, Kruger had not called the apartment- rather, he called a pager. There would be no way to trace the call anywhere other than to the paging company's office.
When a person is defibrillated, the unit fires an instant burst of electricity designed to try and reset a fibrillating heart. When the nurse discharges the unit on Johnny C, the electric hum is heard for several seconds, indicating a steady supply of electricity being sent to the heart. Defibrillators are not designed to do this. Even if a person were cardioverted (the shock being delivered at a certain point during the heart beat or electric cycle), the electricity would be a burst only.
The rail gun shoots a small aluminum projectile at "nearly the speed of light", 186,000 miles per second, or about seven times around the earth in a second. Yet, when the bad guys shoot these things, you can actually see the projectiles flying through the air, they're not even as fast as a cheap BB gun.
Near the beginning of the film, when Kruger is changing the dental records, he uses a graphics tablet and pen instead of a mouse. When he moves the second set of details from right to left, you see him move the pen on the tablet across the middle in one straight, horizontal line but the image on the screen moves from top right diagonally downwards. Unlike when using a mouse, graphics tablets map the screen area exactly, so his pen movement should have copied exactly what we saw on the monitor.
When trapped by the glass door in the weapons building, Kruger stops firing because the bullets are ineffective, not because he has run out. Therefore, a later shot at the sprinkler system without reloading is reasonable.
Lee and Kruger rush from Lee's house just as it explodes, however Lee remembers to grab her purse. In a later scene Kruger burns Lee's ID and Credit Cards. Lee also is in possession of the duplicate disc.
During the opening credits when Kruger is "gearing up" for his rescue mission, the shells that he loads his shotgun with are empty, as evidenced by the two indentations in the primer caps from the firing pin impact. This indicates that they have already been discharged.
In the reptile house, Kruger and Lee crouch behind a low brick wall for several minutes, during which there are a few close-ups showing that a soft-clay brick with bullet strikes has been stretched outward by the squibs exploding inside.