While Atticus does not meet the strict standards of a dynamic character, he does, nevertheless, undergo a chainge in attitude in Chapter 29 of To Kill a Mockingbird when Heck Tate convinces him of the justified reasoning that "Bob Ewell fell on his knife." For, in his discussion with the sheriff, Atticus comes to realize that there is more potential for evil in human behavior than he has hitherto be aware:
Atticus shook his head. "I can't conceive of a man who'd.... "I thought he got it all out of him the day he threatened me. Even if he hadn't, I thought he'd come after me [not his children]."
In another aspect of change involving Atticus, there is much that is revealed about his character to the children and the reader such as his markmanship with a gun. However, the change here is not in Atticus, but in Scout and Jem's attitude toward their father. So, the alterations in the perspective of Atticus must not be confused with a change in his consistently moral, honest, and humble character.
I don’t think Atticus changes much at all over the course of the novel. Throughout the book, he remains morally sound in his thinking and actions and he does this in every situation from the courthouse to his home. If there is any change, it is not discernible. Certainly, he is disheartened by the outcome with Tom Robinson’s trial, but he probably expected this and realized that the social evolution of Maycomb would be a much more gradual process and could not expect a town so steeped in tradition and racist thinking to change over the course of just one trial. He is, maybe, the most forthright and morally justified character in all of American literature. So, as unbelievably good as he is, that’s just the point; he represents ethical justice in totality; he doesn’t need to change.