For Them That Trespass (movie, 1949)

In this drama, a frustrated upper-class writer decides that he will find real inspiration by examining his subjects first-hand. This leads him to begin wandering about the seamiest side of town where he witnesses a murder. When an innocent man is arrested, the writer refuses to assist him as the knowledge that he has been "slumming" could destroy his career. The young man is sentenced to 15 years in prison.