In literature, a dynamic character experiences an internal change that affects their personality, attitude, or perception. Steve Harmon would be considered a dynamic character throughout the novel Monster because he begins to perceive himself differently as he struggles with being identified as a monster. Kathy O'Brien is another dynamic character whose perception and attitude toward Steve Harmon changes as the novel progresses. After O'Brien practices Steve's testimony before he takes the witness stand, she realizes that Steve was an active participant in the robbery and rejects Steve's attempt to hug her after he is found not guilty. Osvaldo Cruz is also a dynamic character throughout the novel. Osvaldo is portrayed as a thug in Steve's flashbacks. However, when Cruz takes the witness stand, he tries acting like a morally upright individual who only participated in the robbery because he was scared. Osvaldo's change in personality makes him a dynamic character.

In literature, flat characters do not experience any emotional change from the beginning to the end of a novel. Sandra Petrocelli would be considered a flat character because her opinion of all the defendants and witnesses does not change throughout the novel. She feels that James King and Steve Harmon are guilty and views them with contempt throughout the entire trial. Richard "Bobo" Evans and James King are also flat characters. They remain callous and mean throughout the novel. They are both portrayed as selfish thugs who do not care about their life or the lives of others.