Inspirations for Billy Jean Davey
Other posters on these boards mentioned the similarity of the plotline to the Michael Kaulhaus story (which also inspired the plot of "Ragtime") and of course to the many stories of outlaw heroes through the centuries, which got me looking at Billy Jean Davey's name and wondered if the screenwriters had in mind the folk ballad of Black Jack Davy? Black Jack was based on a real 17th century outlaw who ran off with the wife of a Lord, who led a gang of men in hot pursuit after the couple. (Black Jack Davy ended up not so well as Billie Jean Davey, though.)
http://en.wikipedia.org/wiki/The_Gypsy_Laddie