While the exact number is unknown, numerous serial killers are never caught. Notable examples of unidentified serial killers include Jack the Ripper, who murdered at least five women in London in 1888; the Zodiac killer, who is believed to have murdered at least five people in northern California between 1968 and 1969; and the Monster of Florence, a killer or killers who murdered at least 16 people in the hills outside Florence, Italy, between 1968 and 1985. The latter case inspired Thomas Harris’s novel Hannibal (1999).
Learn about five notorious cold cases in the United States.