Who is the Zodiac Killer? History's Greatest Mysteries : Season 4 Episode 2

In 1969, a serial killer dubbed The Zodiac Killer taunts investigators with cryptic ciphers, leaving law enforcement and the public questioning his identity for over 50 years. Investigators are hopeful that someday, evidence and technology may be able to crack his identity. Presented are the top six theories of who this mystery man might be. Law enforcement does have a partial DNA match of the killer that was obtained from the back of a postage stamp.