This film sits uneasily in the 30s genre of the "social problem film": uneasily because, though the film does call attention to a pattern of social injustice--in this case, lynching--it goes beyond didacticism in its consideration of violence and revenge. Much of the emotional content of the film is in line with Fritz Lang's concerns throughout his career as a filmmaker, in both Germany and the USA. Lang observes Hollywood conventions for the most part, but still infuses the film with a lot of personal imagery: in the shots of trains near the beginning of the film, in the use of intellectual montage (such as the chickens clucking as an Eisensteinian parallel to the women gossiping), in the montage sequences depicting Joe Wilson's inner torment, in the use of intense close-ups (especially those on both Katherine and the lynchers in the scene where the jail is destroyed), in the contrast of large crowds and isolated individuals, and so on.
Consider the 2-part structure of the film, with one climax in the lynching scene, and another at the end of the trial. The film seems to lurch between its powerful set pieces and the more Hollywoodishly familiar bits of business in between. How is the film unified, if it is?
Consider how Lang draws out Tracy's performance as Joe Wilson, and particularly how Tracy moves from the innocence and naivete of the first part of the film, to the torment and vengefulness of the second part.