Some of the Zodiac Killers cyphers and crytopgrams were so complex that they remain unsolved to this day

Dennis Rader (BTK) studied for a degree in administration of justice, a course that covers the intricacies of the criminal justice system

While investigators were struggling to catch a serial killer in Washington state, they received a letter from Ted Bundy offering his services

Serial killers are often known for their cunning and intelligence, but some have very low IQ scores or get caught in stupid ways

The remains of 26 bodies were found in the crawl space beneath John Wayne Gacy's home

In September 1978, Alcala went on the television show 'The Dating Game' to try and win a date with the bachelorette

Jimmy Savile's crimes were only made public after his death, but a lot of people knew what was happening at the time

Many people consider the United States of America as the home of the modern serial killer. Several of the most well-known repeat murderers were born and operated in the US.

In June 2014, Rolf Harris was found guilty of 12 counts of indecent assault and sentenced to over five years in prison

As brand new recordings of conversations between Dahmer in his lawyer are released, here are 9 of the killer's most-chilling quotes