A man found guilty of murdering his partner's three-year-old daughter has been told he must serve at least 20 years behind bars.
Delroy Catwell, aged 31, was given a life sentence and told he will only be released when he is no longer a danger to the public.
Imposing a mandatory life sentence, Judge Nicola Davis said: "It is difficult to conceive of a greater abuse of trust than than which you perpetrated in killing this vulnerable and defenceless young girl."
Catwell was alone with Lylah Aaron at their home in Sheffield when he subjected her to what police called a 'forceful and sustained attack'.
It was alleged he resented the girl because she was getting more attention from her mother than him.
Earlier, Sheffield Crown Court heard that Catwell, Lylah and Precious Chibanda shared a house in the Shiregreen area of Sheffield.
On February 8, Catwell was left in charge of Lylah as her mother went to work at Derby Royal Infirmary as a trainee nurse.
The court heard how her mother returned later to find her daughter in bed and only later realised she was unconscious. She had suffered serious head injuries and died later in hospital.
Experts said Lylah suffered a brain injury consistent with being hit by a hard object.
The post-mortem examination revealed her injuries were caused by 'repeated impacts to her face and skull'. It also found bruises on her body consistent with being punched, kicked and slapped, and she had three broken ribs.
The examination showed she had been attacked before, the jury was told.
Forensic examination of a bedroom in the house suggested damage to a wall had been caused by someone smashing Lylah's head against it.
The jury heard how Catwell had complained about being sidelined as his girlfriend gave more attention to her daughter.
He described Lylah as demanding and clingy with her mother, taking time away from his relationship with his partner.
Catwell, 31, denied murdering Lylah but was found guilty by a jury at Sheffield Crown Court after a day of deliberations.
When Catwell gave evidence he tried to blame Ms Chibanda for attacking her daughter.
The judge, Mrs Justice Nicola Davies, said she will sentence Catwell today (Weds).
Detective Superintendent Dave Barraclough, who led the investigation, said: "This has been a particularly harrowing case for all concerned.
"Lylah was a happy, innocent girl who was much loved by her family. Only a day before she was seen running and skipping around, like any other child of her age.
"It's horrific that she was viciously murdered by Catwell, a man who should have been caring for her. "I would like to extend our sympathies to Lylah's family at this difficult time."
The officer added: "This murder was a forceful and sustained attack on a defenceless three-year-old girl."
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