Revealing mistake: In the scene where Herbert and Dan re-animate the dead corpse, watch closely when Herbert rams the little buzz saw into the corpse's chest. At the bottom of the screen, you can see where the fake chest ends.
Continuity mistake: The glass window in the door to Dr. Hill's office is broken so that the main character and his girlfriend can enter. Later when Dr. Hill and his severed head return, the glass is perfectly fine.
Continuity mistake: When Cain and West are in the morgue trying to re-animate the cadaver, a phone rings outside at the security desk and when we see it, the buttons are facing outward, but when Megan goes down to the security desk, we see the phone is now turned completely around. (00:49:32 - 00:56:54)
Visible crew/equipment: In the scene where doctor Hill's body is walking about on its own in the lab, it is more than obvious that there is a crew member stood behind it, pushing it forward.
Character mistake: When Cain is attempting CPR on the flatlined patient at the beginning of the film, he tells the other doctor, "She just needs a little more time for the drugs to circulate." Circulation stops at the moment of flatlining. (00:05:25)