Other mistake: When we see the numbers for the coded entry to Alice's weapon, the order of the numbers is 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 0 - 9. The 9 and 0 are the wrong way round. (00:47:40)
Other mistake: When the train arrives back under the mansion from the Hive, it enters the station from the wrong direction. Looking at the track from the platform, the train comes in from right to left, when it should be from left to right. (01:27:20)
Other mistake: Watch Milla Jojovich's hair during the scene when they are held at gunpoint by Spence. Her hair moves from shot to shot. For the most obvious, watch right after Spence shoots the zombie. (01:15:25)
Other mistake: During the scene with the laser, the laser moves along the floor where the EMP device is located, several times. However, when Kaplan and Alice enter the room, the bag with the EMP unit is still intact. (00:31:15)
Other mistake: The elevator is falling to the floor and so the counter weight is going up. But the counterweight doesn't fall back down after all the cables have snapped. What's holding it up? (00:05:55)
Other mistake: Why does Rain get out her torch and hold it with her teeth before climbing under the train? It would have been easier to leave it in her pocket until after she climbed down. We also see, when she is working, that it has a device on the end for gripping it properly with your teeth (called a Lite Bite, I believe). Yet earlier she chooses to grip it by the barrel. Try it with a mini Maglite. It's not comfortable. (00:15:50)
Other mistake: In the laser room everyone is lay on the floor to avoid the first laser. However in a shot from behind Alice you can see that someone is stood by the door in the corridor. (00:32:00)
Other mistake: In the beginning when Spence breaks the T-Virus vial, its fumes can be seen entering the ventilation system from holes on the wall. Shortly after though, when Dr. Blue, Dr. Brown and Dr. Green are trapped in the flooded room, the former of them claims it is "sealed." (00:03:05)
Answer: Actually the T-Virus was originally meant as a cure for a genetic disorder that Dr. Ashford and James Marcus daughters suffered from. The reanimation was a side effect and James Marcus was killed by Dr. Alexander Isaacs so he could take control of it and turn it into a bio-weapon.
lionhead