Revealing mistake: Toward the end of the film, when the bad guys have invaded the good guy's camp, note the scar on the forehead of the lead baddie. The prosthetic scar is very obviously not real.
Revealing mistake: When Ray Liotta's character fights the "lifeguard", the blade on the end of his spear is obviously made of rubber.
Audio problem: When the good guys finally get the Chevy V8 running, the sound it makes sounds more like a moped than a high-performance engine. It has headers and no mufflers, so it should have been quite loud.
Continuity mistake: When the good guys take over the helicopter at the end of the movie, they kill several of the guards and overpower the rest. They force the warden off the chopper, then take off without him. They also leave behind King, who has been a traitor to the group and killed one of them. First of all, when they take off without King, he seems surprised that they don't take him along. Secondly, when the 'copter flies away, we see King and the warden standing alone in the clearing. What happened to the half-dozen or so guards?
