Factual error: At the end, Denzel Washington's character has a Grand Mal Seizure. But he is supposed to have a spinal cord injury. He can still have seizures in that the electrical impulses in his brain go haywire, but if he has a spinal cord injury that prevents him from moving, the seizure action in his brain wouldn't translate to his body jerking and shaking.
Continuity mistake: In the scene where Amelia is driving the truck full of policemen to the scene of the second (Mrs. Rubin) murder, the shot changes a couple of times before it settles looking through the front windscreen at Amelia. Through the rear windscreen of the truck, you can clearly see the highway and all the cars on it behind them. Amelia turns the steering wheel sharply to the left, and you hear the screeching rubber-tyres-on-tarmac noise as if she really had swerved left, but the scene of the highway behind them seen through the rear screen does not alter at all - as if she was just going in a straight line all the way.
Trivia: The movie makers really wanted the audience to believe that Michael Rooker was the killer, rather than Leland Orser. So much so that Rooker actually played the killer in almost all the scenes where the killer wears a mask. When you see the eyes of the killer through the mask the eyes are Rooker's.
Lincoln Rhyme: Whatever happened to your father doesn't mean it's gonna happen to you. You're a great cop. You'd make a terrific detective. It's a gift. Don't throw it away.
Amelia: I can't do this.
Lincoln Rhyme: You can do it. Yes, you can. Yesterday you stopped a train. You can do anything you want when you put your mind to it.
Amelia: Don't work me, Rhyme... Just tell me what to do next.
Lincoln Rhyme: Very slowly... walk the grid... one foot in front of the other. I want you to look around you now. Remember... crime scenes are three-dimensional... floors, walls and ceilings.
Amelia: Excuse me, but the victim was already dead when we arrived.
Captain Howard Cheney: And you, half-assed patrolman working a crime scene... those days are over. I'll take that evidence bag now, thank you.
Amelia: You can take it with a chain of custody voucher, sir.
Captain Howard Cheney: Are you out of your mind? Hmmm? Let's go. You're coming with us.
Amelia: What? Are you arresting me?
Captain Howard Cheney: You just get in the car, and keep your mouth shut to the press.