The flashback scenes were usually shot with the type of film stock used at the time of the setting (as much as possible).
Justin Chambers was originally part of the main cast, appearing in the first 4 episodes of season one before leaving to take a role on Greys Anatomy. Danny Pino was hired several weeks later as Chambers replacement.
Songs played in each episode generally come from the year the crime took place, with some notable exceptions where the soundtrack features a particular artist or theme, instead of a year: Season six, episode eleven, "Wings" featured the music of Frank Sinatra. The season five opener "Thrill Kill" features only Nirvana tracks. Season four featured episodes containing the music of U2 and Bob Dylan. Season three featured episodes containing the music of John Mellencamp and Bruce Springsteen, as well as episode eighteen, "Willkommen", which featured music from "Cabaret". Season two had an exclusively Johnny Cash themed episode, as well as episode twenty-one, "Creatures of the Night", which was set around The Rocky Horror Picture Show (1975) theatrical phenomenon, and features music from the film soundtrack.
Due to the use of contemporary music in each episode, none of the seasons are available on DVD because of music licensing issues.
Actor Danny Pino, who played co-star Detective Scotty Valens, wrote for a number of Season 7 plots, including a story about a Cuban refugee, as well as one about a young circus aerialist, the latter of which featured a soundtrack by The Doors, Pino's favorite band.