Continuity mistake: When Portnow meets with Bishop at the church, in the first closeup of Bishop's crossword puzzle the word "MUD" is the second word across at the top, and at the center of the puzzle the 4-letter word "GEAR" is written in the 5-letter answer - with the fist space left empty. However, in the next closeup of the puzzle, now the word "ETA" is the second word at the top and "MUD" is the third, and the word "GEARS" has the "S" added, with the letter "G" started properly in the first space of the answer. (00:10:15)
Continuity mistake: When Beck is shot outside the Precinct, from the front view he has no exit wound on his forehead. Yet when he lands on the snow a few seconds later, an exit wound has appeared.
Continuity mistake: During the entire movie it is snowing heavily. At the very end, when the last shot pans over the city there is no snow anywhere, not even on the trees.
Continuity mistake: During the outdoor scenes throughout the movie, and most noticeably during the forest scenes, condensation from the actors' breaths appears almost randomly. Sometimes their breaths can be seen in the cold air, and other times not at all.
Continuity mistake: Sgt. Roenick's facial hair changes throughout the movie. Most of the time it is seen as a scruffy moustache and goatee, several days worth of growth. But in the scene where he tells the prisoners the precinct is under attack by rogue cops, he is practically clean-shaven. And during the scene in the forest, he is sporting a five-o'clock shadow instead of the usual goatee.
Continuity mistake: Near the end of the movie when the marked Detroit police car arrives and skids to a stop you can see the marks from a previous take in the "snow".
Continuity mistake: When "8 months later" appears on the screen, we see Jake's nightstand with only one framed photograph near the lamp as the camera pans to the right, but in the next wideshot that photo has moved to the front of the lamp and two more framed photos have suddenly appeared. (00:05:30)