1: One of the major motifs I noticed was the idea of Perseverance and Survival. His fight for his own freedom, his fight to stay strong, and his fight for the truth is the major motif of the film. Carter is a fighter - even after two juries reviewed his case, both of whom pronounced him guilty, he continued to fight to get out of prison and to keep strong whilst confined.
2: 1st Symbol: The typewriter and letters. The fact that Esra and Carter can communicate to each other, expressing their feelings, hopes, and dreams, even from so far away (and when one is behind bars), shows the remarkable power of the written word. That so much could be transferred by ink upon a page is a way for both Esra and Rueben to fight - and a small crack in the walls that have held him back his entire life.
2nd Symbol: On the same topic, is the idea of jail. Until the end of the movie, Rueben has been behind a wall all his life, preventing him from experiencing life to the fullest. This is so, not just literally, but metaphorically as well - his race was a sort of barrier to him - and just as the walls and bars surrounded his cell, an invisible wall keeps him away from the full enjoyment of life, simply because of his race.
3: One major part, one of significant importance, within the various legal proceedings, is Rueben's calm demeanour. Through the entire procession, when the entire audience, jury and opposition is becoming emotional, he remains calm. This shows Carter's grim acceptance of his fate - he knows that he will be convicted, so he must not show any sort of emotion. If he did, it would make him look weak - and it would make it even harder for him to get out of prison.
4: One that you could notice is a combination of the two main motifs of the book and movie: fighting for justice, no matter whether you're going to win. This is why Atticus took on Tom Robinson's trial, and why Rueben kept on fighting for freedom; they both possessed a determination to fight for justice and truth, no matter the odds against them or the cost.
