The scene where Manny (Henry Fonda) is taken to prison was filmed in a real prison. As he is led to his cell, one of the inmates can be heard to yell out, "What'd they get ya for, Henry??", and a bunch of the other prisoners laugh.
Sir Alfred Hitchcock utilized some of the real locations where the events took place, including some of the real witnesses. Among these are the jail cell where the Manny Balestrero was incarcerated, the caretakers at the country inn and the inn itself, and the sanitarium where Manny's wife was committed. As much as Hitchcock hated filming his movies on location, he felt that authenticity was crucial to this film due to its real-life "elements that are stranger than all the fiction".
Although based on a true story, Sir Alfred Hitchcock deliberately left out some of the information that pointed to Manny's innocence, to heighten the tension.
This movie is one of Martin Scorsese's favorite Sir Alfred Hitchcock movies, and was an influence on Taxi Driver (1976).
On the DVD, the running commentary revealed that when the crew went to film the scenes at the country hotel, Sir Alfred Hitchcock stayed in his limo due to the cold outside and decided to move the production to Hollywood to complete the movie.
Alfred Hitchcock: Narrating the prologue. This was the only time that he spoke in any of his movies.
Alfred Hitchcock: Hitchcock filmed one of his usual cameos, standing in a restaurant as Manny sits, but decided on using a narrated prologue instead, believing the levity of a cameo worked against the serious tone of the film.