19. The case of the zodiac killer
The case of the zodiac killer comes next in this list. It is a highly intriguing event which actually took place between 1960s -1970s. During this time, a criminal mastermind emerged who was notoriously nicknamed as the zodiac killer. He was named this because of the zodiac letters he would send to the press and police. Among many of these letters only four letters could be decoded by experts.