A teenager killed an 11-month-old baby because he resented the way she got in the way of his relationship with her mother.
Mitchell Cooper, 17, swung Ruby Spink against a wall in a jealous rage, then calmly called paramedics and claimed she had choked on a piece of cake.
The infant died the same day in hospital - two months after social services began 'closely monitoring' her following a tip-off and six days after she was placed on an at-risk register.
A post mortem revealed she had suffered broken legs and ribs in the weeks before her death and had been shaken violently.
Ruby's natural father, Martin Shabangu, yesterday accused social services of failing her as Cooper - who denied murder - was jailed for life and ordered to serve at least 12 years.
The baby's mother, 18-year-old Laura Spink, was sent to a young offenders' institution for 12 months after admitting neglect.
'They could have taken action as soon as they saw things happening,' said Mr Shabangu, 25.
'They should have taken her away [from them] or given her to me. They were willing to do that but gave Laura a second chance.'
Norwich Crown Court heard that Spinks, who lived in a hostel in Great Yarmouth, had been out shopping with her child on September 16 last year.
She returned home at lunchtime and left Ruby with Cooper, who was playing on a Playstation.
Paramedics were called shortly afterwards and Ruby died in James Paget Hospital in nearby Gorleston at 4.05pm.
Tests revealed a fatal blow to the head, which caused a six-inch skull fracture and brain injuries.
Other 'historic' injuries were spotted and an eye specialist later told detectives that heamorrhaging behind the girl's eyes showed she had been violently shaken in the past.
Further enquiries revealed witnesses had seen Cooper treating Ruby 'roughly' and one had seen him swinging her around by her legs.
Both Cooper and Spink, who were unemployed, were also discovered to have racially abused Ruby, who was of mixed race.
They teenagers were both arrested on September 20.
Cooper, of Great Yarmouth, admitted during a police interview that he had teased Ruby 'like a dog' with food but stuck to his story that she had choked to death.
During the trial, the jury heard heard the child had been examined by a GP and two specialists in the weeks before her death but while all of them noted injuries, none of them noted anything suspicious.
Sentencing Cooper yesterday, Judge Peter Jacobs told him: 'You just lost it. You resented the child. Your dislike of the child came to the surface.
'You forcibly banged this child's head against a hard surface. As a result of that you caused a fracture to the skull, which resulted in death.'
Addressing both teenagers, he added: 'You're both the victims of deprivation but there's nothing in your background which justified the way you treated this child.'
Speaking after the case, Detective Inspector Andy Guy said Cooper had never shown remorse.
'He is a violent and immature man whose brutal actions left a defenceless child in significant pain and ultimately lead to her death,' he added.
Ruby's death will raise disturbing questions about whether lessons have been learned from the case of Victoria Climbie, who died in February 2000 aged eight.
She had been starved, beaten, bound naked and kept prisoner in a freezing bathroom in a squalid flat in Haringey, north London.
Following a year-long public inquiry, Lord Laming highlighted a catalogue of errors and said Victoria could have been saved if police, social workers and doctors had done their jobs properly.
He went on to make more than 100 recommendations for reform but one child a week is still falling victim to murder or manslaughter, many of whom come to the attention of social services.
Norfolk County Council's deputy director of children's services, Meera Spillett, yesterday said: 'Based on his background, Cooper had been assessed as low risk.
'During the course of his trial, several witnesses have spoken of his ill treatment of Ruby. We heard most of this evidence for the first time in court.
'The court also heard that no residents at the hostel where Ruby and Laura were living ever complained to either us or the police about his treatment of Ruby.'
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