The piece of music that Lou (Casey Affleck) plays on his piano is the 25th variation of J.S. Bach's Goldberg Variations. It was regarded by musicians, such as Glenn Gould and Wanda Landowska, as one of the most significant pieces of music ever written, even within the context of the entire set of variations, which is generally held to be one of Bach's greatest masterpieces. Gould's 1955 recording of this variation was included in the soundtrack to Slaughterhouse-Five (1972), during scenes portraying the firestorm that destroyed Dresden.
Andrew Dominik had written a highly stylized screenplay for the movie in 2003, and was at one point considered to direct it. Not long afterward in 2004, Dominik would accidentally stumble across an obscure western epic novel by Ron Hansen in an Australian bookstore, which he later adapted as The Assassination of Jesse James by the Coward Robert Ford (2007), coincidentally starring Casey in one of the titular roles.
Jessica Alba left halfway through the movie's world premiere at the 2010 Sundance Film Festival. Why Alba left is unknown but, according to critics in attendance, there were quite a few walkouts from folks who found the film's violence towards women disturbing, namely scenes featuring Alba repeatedly punched in the face and taking a ruthless belt-lashing across her nude butt by Casey Affleck.
Based on the book "The Killer Inside Me" by Jim Thompson.
Katherine Heigl, Michelle Williams, Natalie Portman, and Sienna Miller were all considered to play Amy Stanton.