Continuity mistake: At the end of the movie when Gene Hackman is in the bar, his drink is low, it is then double the original size when the others leave. (01:58:55 - 02:01:00)
Continuity mistake: Towards the beginning of the movie when Rankin Fitch is in the cab, watch the meter. They drive only for a few minutes, but the meter never changes from $24.50. (00:08:05)
Continuity mistake: When Marley is walking to meet Rourke at the cafe, look behind her as she turns the corner and comes to a stop. You will see a woman inside the cafe behind her take a sip from her coffee. The scene then cuts to a close-up of Marley and we see the woman inside the cafe take that same sip of coffee again. There was not enough time for her to drop her hand and bring it back up again to take another sip.
Continuity mistake: Gene Hackman meets the head of the gun company where the head guy has his shooting range. After they are done talking, Hackman walks away and the head is in the process of taking out his protective glasses, the shot changes and the head has already fired his weapon and hit his target, while Hackman is the same distance away.
Continuity mistake: When Dustin Hoffman and Rachel Weiss are talking at the coffee shop, Dustin's shirt collar moves from in and out of his vest. (01:23:40)
Continuity mistake: In the final scene, Marlee and Nick are seen together looking at a school yard of children playing while holding each other. Notice Marlee's hair is dark red, then there's a shot to Mr. Rourke and back to Nick and Marlee. Her hair is now black, and then another shot back to Mr. Rourke, and back to Nick and Marlee. Now her hair is dark red again.
Continuity mistake: When Fitch enters the courtroom for the verdict, we see him button up his collar just as he enters. However, after the decision has been made, he stands, and we see that his collar is now unbuttoned.
Continuity mistake: When Nick and Marlee are talking in the church after his apartment is burned, he talks about the danger and she touches his face with her left hand, right hand out of sight below frame. She drops her hand slowly, but as he steps away it is her right hand that is raised and the left lowered. (01:11:40)
Continuity mistake: About five minutes in, John Cusack is talking to the janitor who is clearing weed from the pool of the fountain. The janitor pulls all the weed off the top of the pump, but in the next shot the weed is all back on top of the pump again.
Continuity mistake: In the scene where the jury picks its foreman, Nick Easter raises his hand as he suggests Herman Grimes. The camera pans around the room as the others raise and hold their hands in the air, including Miss Hullic, who is sitting behind Frank Herrara. In the next scene, Frank Herrera looks around at the other jurors and, just before he looks over his right shoulder, Miss Hullic raises her hand from her lap again. (01:17:20 - 01:21:15)
Answer: Jennifer Beals' role is a bit of a misdirection towards the viewer, a little like Janet Leigh in "Psycho". It misleads the viewer into beleiving she might be crucial to the plot.