Fairly early in Just Mercy, an employee of the Monroeville, Alabama, district attorney's office encourages a young lawyer played by Michael B. Jordan to visit the nearby To Kill a Mockingbird museum. It's housed in the courthouse where Harper Lee's father worked, the assistant explains; you can see the place where Atticus Finch once stood. The sly joke, of course, is that Finch is a fictional character.
Not so with this movie's protagonist. Bryan Stevenson really is a Harvard Law graduate who moved to the Deep South in 1989 to represent impoverished death row inmates. He really did found a practice called the Equal Justice Initiative, which has won relief for hundreds of wrongly convicted and unfairly sentenced prisoners—beginning with Walter McMillian, played by Jamie Foxx, an innocent black man who really was framed by local authorities for the murder of a young white woman.
The film is based on Stevenson's autobiography of the same name. If its storytelling suffers for depicting an uncomplicatedly righteous protagonist, it's likely because director Destin Daniel Cretton rejected manufactured drama in favor of fidelity to the source material—the true story of a good man.