A boy has been detained for life for the rape and murder of a 14-year-old girl in a park.
Now 17, his trial heard he "smashed" Viktorija Sokolova's head with a hammer-like object in a "sustained and ferocious" attack on 11 April 2018.
Her lifeless and partially clothed body was found by a dog walker on a bench in Wolverhampton's West Park the next day.
At Wolverhampton Crown Court the boy, who cannot be named, was ordered to serve a minimum of 19 years.
The boy had denied any wrongdoing but was unanimously convicted by a jury at the same court on 17 December last year.
Jurors heard Lithuanian-born Viktorija was lured to West Park late at night after being contacted by her killer on Facebook Messenger.
Once there, the pair met at a pavilion referred to as the "black house", where Viktorija was struck over the head at least 21 times causing multiple fractures to her skull and spine.
The sentencing judge said Viktorija - described in court by her mother as her "one and only" - had been left "degraded" after she was "battered" and her body dragged 150 yards to a bench.
Following the killing, the youth was caught on CCTV as he attempted to cover up the offence by hiding clothing, having already deleted Facebook messages and hurled his victim's phone towards a lake.
Mr Justice Jeremy Baker told the boy he had carried out a "truly shocking attack" on a defenceless and vulnerable young girl after watching pornography and carrying out internet research.
He added: "The offences committed were extraordinarily serious.
"Given the nature both of your personal internet research, and the injuries subsequently inflicted on her, it is clear you had planned not only to rape her but batter her to death with a weapon you'd brought with you, for that purpose."
The weapon used in the attack has not been found.
Adam Kane QC, in mitigation, told the judge the boy had been diagnosed as a paranoid schizophrenic since the end of the trial.
The court heard her killer had claimed the pair had consensual sex and she was "alive and well" when he left to go home.
But police found the mobile phone he used to contact Viktorija in the back of a wardrobe and discovered Facebook Messenger, plus records of calls to and from Viktorija, had been deleted, as had records of searches.
In the hours after the killing he used his brother's phone to search "how to delete your Facebook account permanently" and also filmed himself scrolling through the Notes app on his iPhone as he prepared to delete evidence.
'No tears left'
In a victim impact statement read to court, Viktorija's mother Karolina Valantiniene said her daughter had "many beautiful plans for the future", learning how to drive, finishing school, and she had spoken of "buying her a beautiful prom dress".
"April 12, 2018 was the most horrible day of my life," Ms Valantiniene said.
"I left for work, as normal, and at work was asked to come to the office and - at that moment - my world fell apart.
"I cried out all my tears. It felt like no tears were left."
She added: "I wanted to die together with her. Many times, I've asked why are there such terrible people on the Earth.
"To realise you don't have your child anymore, and never will again."
Despite the mobile phone evidence, the boy's barristers had suggested Viktorija's parents may have played a part in her death after it emerged microscopic traces of her stepfather's semen were found in her underwear.
But the pair were eliminated from police inquiries at an early stage, and forensic experts suggested the transfer of her stepfather's DNA was via innocent means.
Saidas Valantinas said he had no idea why his DNA was on her clothing and said the defence's argument was "unreasonable", "unsubstantiated", and "rude".
The court also heard about his "turbulent" relationship with Viktorija, who was sent to live with her father in Northern Ireland for two months because she repeatedly ran away.
Jurors were told there was also a physical altercation between Viktorija and her mother the Sunday before her murder.
Wolverhampton Safeguarding Board has said it will publish a serious case review looking at Viktorija's contact with the authorities.
Detective Inspector Caroline Corfield from West Mercia Police's homicide unit described it as a "deeply distressing case".
"The murder of Viktorija shocked the local community and the wider general public, not least because of the ages of those involved," she said
"As many young teens do, Viktorija was testing boundaries and could be wilful, but she was a popular girl and had the love and support of her family and friends.
"She certainly had her whole life ahead of her, but sadly that was brutally cut short."
Follow BBC West Midlands on Facebook, on Twitter, and sign up for local news updates direct to your phone.