A dynamic character changes over the course of a story in a significant way. It’s an important thing to look at it because character changes usually tell us something very important about the theme of the story. In To Kill a Mockingbird, it is significant that Jem is a dynamic character.
For much of the story Jem does not seem dynamic. He is frequently at odds with Atticus about issues that he doesn’t understand. However, by the end of the novel, after Tom Robinson’s trial, and his experiences with Dill and Mrs. Dubose and Boo Radley, we begin to see that Jem has become more thoughtful about life. We see this in chapter 23 when Jem says this about Boo:
Scout, I think I’m beginning to understand something. I think I’m beginning to understand why Boo Radley’s stayed shut up in the house all this time . . . it’s because he wants to stay inside.
This marks a major passage into maturity for Jem. Until this point, he was content to consider Boo a monster, a freak. But now he has learned the value of his father’s advice, which is to always consider a person from their own perspective.
In Harper Lee's To Kill a Mockingbird, which is a bildungsroman or novel of maturation, Jem Finch is certainly a dynamic character; that is, he is a character who experiences an essential change in his perspectives and attitudes.
While some of Jem's character change is due to normal maturation, there is also an attitude change in Jem. Early in the narrative, as an imaginative boy Jem joins in the antics of Dill (Charles Baker) Harris, whose creative ideas include re-enacting the life of Boo Radley and peeping into the Radley home. But when Jem and Scout find two soap dolls in the Radleys' tree, Jem is struck by the artistry--the figures resemble him and his sister. He is touched, as well, by the significance of this act of friendship; he places the soap figures in his chest and changes his attitude about Boo Radley, starting to understand the shy man who so kindly has placed a blanket on his sister as they stand in the cold while Miss Maudie's house burns.
In the final chapters, Jem surely appreciates Boo Radley as Boo prevents Bob Ewell from attacking and harming him and his sister. This is a complete change of perspective from his views in the early chapters.
In addition to altering his attitude about Boo Radley, Jem changes in his perception of his father. Whereas he has felt that Atticus is old and cannot do much, after "one-shot Finch" saves the day by shooting the rabid Tim Johnson, Jem is so impressed by his father's skill that he exclaims, "Atticus is a gentleman, just like me!" He picks up a rock and throws it in jubilation. Jem also realizes that Atticus is such a superior shot that he does not want to shoot animals, because he has an unfair advantage over them.
Perhaps the greatest challenge to his development comes when Jem attends the trial of Tom Robinson. After listening to the testimony and the cross-examination by his father, Jem believes that Tom will be found innocent based upon the fact that Mayella seems to have been beaten by her father and Tom's testimony establishes his innocence. As Atticus has established, it appears that Mayella has been beaten by a man who used his left hand on her. But Tom has a withered left arm that "hung dead" at his side and a shriveled hand, making it impossible for him to have hit Mayella where her injuries are visible.
The Reverend Sykes, who understands the reality of life in Maycomb, tries to tell Jem not to be so confident in his conclusions, but the innocent Jem does not understand. Consequently, Jem becomes very disillusioned by the outcome of the trial.
It is after hearing the verdict that Jem becomes an adult, perceiving the incongruity of events and subsequent actions in real life. He repeats that the verdict against Tom Robinson "ain't right." He no longer thinks Maycomb folks are "the best folks in this world" as he previously stated, and he tells his sister that he now understands why Boo Radley remains inside his house.
Fortunately, Jem talks with his father, who points out to his son that there has been some progress in their society; the jury did not immediately reach their verdict. After their conversation, Jem begins to cope with his disappointment, and he matures as he becomes aware of the realities of life.