Jared Poe, who plays FBI Cadet Rudolph Hayes, was a WGA intern working in the writing staff office. He asked Frank Spotnitz for permission to audition for an acting role, and Spotnitz reluctantly agreed. Despite his lack of formal training, Poe beat out the approximately 30 other actors who auditioned for the role.
Robert Patrick found the final scene - in which his character John Doggett scatters the ashes of his dead son - to be extremely difficult to film.
One of the suspects Doggett interviews calls him a "flatfoot." Flatfoot is a slang term for police officers that has been used since the early 1900s. While the exact origin of the term is not known, it likely referred to the large amount of walking police officers do, especially at the turn of the century when most cops didn't have cars. At the turn of the 20th century the condition of flat feet had become widely known, and one of the causes of it was thought to be excessive walking. Another possible origin of the term is during both World Wars the Army would reject men with flat feet because they could not run well; a lot of the men who were rejected by the Army because of flat feet took jobs in law enforcement because a lot of the established police officers during the wars either joined the military or were drafted, thereby creating a need for a large number of replacement officers.
John Shiban originated the idea for the episode, handing over the writing duties to his co-writer, David Amann.