Mary Flora Bell

In 1968, a 10-year-old girl named Mary Flora Bell killed two boys. She and her accomplice strangled the second kid to death and carved their initials into his stomach and mutilated his genitals. The crime scene was described by the inspector as “There was a terrible playfulness about it...and somehow the playfulness of it made it more, rather than less, terrifying”. Psychological testing revealed she was a sociopath. She was convicted and then released at the age of 23 under a new identity.