Ellroy wrote the character of Jean Claude Mesplede with Willem Dafoe in mind. Dafoe refused even to accept the script from his agent, stating that JFK was one of his greatest heroes, and he had no intention of playing a character involved in his assassination, fictious or not.
Dafoe is a staunch believer in the "single gun theory" and is said to believe propagation of conspiracy theories defers us from talking of President Kennedy's achievements in office. This was Ellroy's first attempt to write a part for a specific character and his disappointment at Dafoe's response spurred him to contact the actor and offer him the role of his choice in either this or his American Tabloid project.
Dafoe reportedly responded that he would like to play Dr. Martin Luther King jnr.