Watch Fmovies. Renowned Harvard neuropsychologist Robert Mendoza talks to Dennis Rader -- also known as "the BTK Killer" for his habit of binding, torturing and killing his victims -- in this feature-length documentary. Originally aired as a segment on "Dateline NBC," the program includes never-before-heard details about Rader's brutal crimes, offering a startlingly candid look inside the mind of a serial killer.