Mary Bell
The English girl was just 11 years old when she strangled two young boys (three and four years old) to death in 1968. After killing the younger of the two victims, Bell reportedly returned to the scene and carved the letter “M” into the boy’s stomach with a razor. She was released from prison in 1980 at the age of 23, and has lived under court-protected anonymity ever since. Cries Unheard: The Story Of Mary Bell, a book about her life, was released in 1998.