[5][6] Bell was convicted of manslaughter in relation to both killings in December 1968, in a trial held at Newcastle Assizes when she was 11 years old, and in which her actions were judged to have been committed under diminished responsibility.

[2] For most of her life, Mary believed her father to be William "Billy" Bell,[14] a violent alcoholic and habitual criminal with an arrest record for crimes including armed robbery.

According to her aunt, Isa McCrickett, within minutes of Mary's birth, her mother had resented hospital staff attempting to place her daughter in her arms, shouting: "Take the thing away from me!

[20] Both at home and at school, Mary exhibited numerous signs of disturbed and unpredictable behaviour, including sudden mood swings and chronic bed wetting.

This violent behaviour made many children reluctant to socialise with Mary,[22] who would frequently spend her free time with Norma Joyce Bell (1955–1989), the 13-year-old daughter of a next door neighbour, with whom she had become acquainted in early 1967.

Both girls denied any culpability for the air raid shelter incident, claiming they had simply discovered the boy, bleeding heavily from a head wound, after he had fallen.

Many inner boroughs of the city saw Victorian-era terraced slums demolished in order that modern houses and flats could be constructed, although several families resided in buildings earmarked for demolition as they awaited rehousing by the council.

[27] Local children frequently played in or close to the derelict houses and upon the rubble-strewn expanses of land razed and partially cleared by contractors.

[30] On 25 May 1968, the day before her 11th birthday, Bell strangled four-year-old Martin Brown in an upstairs bedroom of a derelict house located at 85 St. Margaret's Road.

The two entered the premises by peeling tiles off the slate roof; they tore books, upturned desks, and smeared ink and poster paints about the property before escaping.

[37][n 2] Two days later, on 29 May, shortly before the funeral of Martin Brown, in a game of chicken,[39] both girls called upon the house of his mother, June, asking to see her son.

[42] The first policeman to arrive at the scene observed that a "deliberate but feeble" attempt had been made to conceal the body, which was covered in clumps of grass and weeds.

Numerous puncture wounds had been inflicted to the child's legs before death, sections of his hair had been cut from his head, his genitals had been partially mutilated, and a crude attempt had been made to carve the initial "M" into his stomach.

This self-incriminating statement convinced Detective Chief Inspector (DCI) James Dobson that Mary was the actual killer, as only the police knew about the broken scissors found at the crime scene.

In addition, the local boy she named was quickly questioned, and was discovered to have been at Newcastle International Airport on the afternoon of 31 July, with numerous witnesses able to corroborate his parents' claims.

[46] On the afternoon of 4 August, the parents of Norma Bell contacted police, stating their daughter wished to confess what she knew of the death of Brian Howe.

According to Norma, Mary had confessed to her she had enjoyed strangling the child, before describing how she had inflicted the scour marks to his stomach with a razor blade—which had been hidden at the crime scene—and "the broken scissors".

According to Norma, when the trio were alone on the "Tin Lizzie", Mary "seemed to go all funny", pushing the child into the grass and attempting to strangle him before stating to her, "My hands are getting thick.

According to DCI Dobson (who had planned to arrest both girls later that day), Mary Bell stood outside the Howe household as the child's coffin was brought from the home at the beginning of the funeral procession.

She also admitted she and Norma had broken into the Woodland Crescent nursery the day after the killing of Martin Brown, defacing the property before the two had written the four handwritten notes.

In his official report compiled for the Director of Public Prosecutions, David Westbury concluded: "[Mary's] social techniques are primitive and take the form of automatic denial, ingratiation, manipulation, complaining, bullying, flight or violence.

[55] As such, the media were allowed to publicise the names, ages and photographs of both girls, who each sat alongside plainclothed female police officers in the centre of the court, behind their legal representatives, and within arm's reach of their families throughout the duration of the trial.

In an opening statement lasting six hours, Lyons informed the jury they faced an "unhappy and distressing" task due to the nature of the murders and the ages of the defendants.

A child psychiatrist named Ian Frazer then testified that Norma's mental age was eight years and ten months and that, although her capacity of knowing right from wrong was limited, she was capable of appreciating the criminality of the acts she was accused of committing.

Robson also referenced the testimony of David Westbury,[62] who had testified on behalf of the defence he had interviewed Mary on several occasions prior to the trial and had formed a "definite view" the child suffered from a serious personality disorder which he classified as a "retarded development of (her) mind", and that this had been caused by both genetic and environmental factors.

[4][n 5] Passing sentence, Mr Justice Cusack described Bell as a "dangerous" individual, adding she posed a "very grave risk to other children"[66] and that "steps must be taken to protect [the public]" from her.

[64] At the time of Bell's manslaughter convictions, she was aged 11 years and six months, making her Britain's youngest female killer, a statistic which remains to the present day.

[75] Bell was arrested at the Derbyshire home of one of the men, Clive Shirtcliffe, on 13 September, having by this stage dyed her hair blonde in an effort to disguise her identity.

[80] Beginning in November 1979, Bell worked first as a secretary, then as a waitress at a café in York Minster under supervision guidelines in efforts to prepare her for eventual release.

Her daughter knew nothing of her mother's past until 1998, when reporters discovered Bell's then-current location in a resort town on the Sussex Coast,[82] where both had been living for approximately 18 months.