Duffy is based upon the true to life character, Albee Baker. The story actually happened in the mid Fifties and was recounted by Albee to the writer, Pierre de la Salle who came to know Baker in 1956 while living in New York.
When Duffy and Segolene have their conversation near the end, when she tells him she belongs to no one, her position changes between shots, from standing near the edge of the roadway to moving a good 10 feet closer.