Just watched Badlands this evening, Terrence Malick's 1973 film with Martin Sheen and Sissy Spacek. It's loosely based on the Charles Starkweather/Caril Ann Fugate murders. I highly recommend it, mainly because Sheen is so charismatic that he makes the killer likeable. It's truly a model for how to create sympathetic characters, by convincing the audience to like the character, even if he's despicable.

Along with this movie, I'd also recommend Liza Ward's 2004 novel, Outside Valentine, which is fictionalized account of the same murder spree, set in three time periods and told in three alternating voices--the voice of Caril Ann, which is definitely the most haunting, the voice of two of the victims' son, and the voice of his future wife. An eerie and utterly convincing read. More information about the novel is at Henry Holt, here. A good interview with Liza Ward is here.