A trio of codebreakers have managed to crack a coded message written by one of America's most notorious serial killers. The 340-character message in question was sent to the San Francisco Chronicle more than 51 years ago by the so-called Zodiac Killer. The murderer, who has never been caught, killed at least five people in the 1960s - and has claimed responsibility for another thirty deaths. Melbourne mathematician Sam Blake is one of the three men who cracked the code.