Momb does have a point. Compare the Bell case and the Venables/Thompson case.
Mary Bell was 11 and charged with killing two boys, aged three and four, by strangling them to death. She later claimed to have been abused by her mother throughout her childhood. Her mother was a prostitute and apparently Mary was also abused by her mother's clients.
Venables and Thompson were one year younger and killed one boy. Thompson seems to have come from an abusive household, just like Bell, but Venables possibly not.
Yet Bell was only charged with manslaughter and not murder, on the grounds of diminished responsibility, was regarded as probably psychopathic and a danger to other children. After serving 11 years she was released, granted a new identity and is now a mother herself and apparently a normal member of society.
Interestingly, she was initially held in the same secure unit that Venables was held in.