To reflect the characters feelings and changing world-view, directors use techniques that portray characters’ internal world. After John Doe turns himself in, in the police car, the shots show Detective Mills’ confusion by showing him behind the car fences just as they do it for John Doe. This shows what Doe says is influential to Mills and this will later be proven. On the other hand, Detective Somerset is never shown behind the fences, showing he is more stable when it comes to his world view.
During the chase scenes, we see the characters’ personality. For instance, the shots showing Detective Mills are from different angles and shaky. This basically tells Mills’ instability.
Later in the story (near the end), when Mills is about to kill Doe, we see the gun pointed at us. This could mean that either the society is in the wrong when it comes to embracing those who are confused.
During killing scene, we see Doe from different angles mostly in close-ups. In one of the scenes, we see his head covering the sun as if his soul is about to be let free. Also, they are steady with little to no move. We can interpret this part as him being alright with the situation and ready to die. Mills, on the other hand, is unstable because, first we can see it by looking at him, and second the shots are unstable.
The dialogues also conforms the 180° rule. They are on a single line, helping the audience where they are in the story.
At some point, just before Mills kills Doe, we see a glimpse of Mills’ wife, Tracy, which shows the reason why Mills will fail to handle the situation and be part of Doe’s evil plan by completing it.