Mary Bell was 11 when she was given a life sentence in 1968 after being found guilty of the manslaughter of four-year-old Martin Brown, and Brian Howe, 3, on the grounds of diminished responsibility.
CNN's Ben Wedeman, Ben Brumfield, Marilia Brocchetto, Sarah Brown, Dugald McConnell, Brian Todd, Claudia Rebaza and Jason Hanna also contributed to this report.