Whilst this is quite a well-made film, full of corrupt characters and a sleazy atmosphere, it's plot becomes clear within the first 5 minutes.
Sure, the two adult survivors of the hijack/ambush/crash/disaster are lying about what happened, but they have good reason to. Sure, the police department is full of wierdos with no sense of right and wrong. But, you can tell that everyone is lying very quickly as the film justaposes reality with testimony, and this should lead to some obvious conclusions quite quickly.
Other reviewers say there is a great twist at the end of the film. The 'twist' isn't at the end, and it's not a 'twist' it's more of a reveal, a confirmation of what you should already know if you've been paying attention.
The redeeming feature of this film is the direction, which slowly builds the atmosphere, taking it's time to create a semi-believable situation. This isn't a fast-paced thriller, and the gore could have been cut out completely and the film would be just as good, but the slow pace, less than perfect characters and the claustrophobia of the police station are worth the price of admission.