A 16-year-old boy who killed a schoolgirl and dumped her body on a park bench has been found guilty of rape and murder.

The boy, who cannot be named because of his age, remained composed as a jury at Wolverhampton crown court unanimously convicted him of murdering Viktorija Sokolova.

Detectives believe the boy used a hammer, which has never been found, to attack the 14-year-old, who suffered a fractured skull and spine.

A three-week trial was told that Viktorija was lured to West Park in Wolverhampton late on 11 April after her killer contacted her on Facebook Messenger.

He was caught on CCTV after the killing as he attempted to cover up the offence by hiding clothing. He also deleted Facebook messages and hurled his victim’s phone toward a lake.

Detectives also achieved what is thought to be a legal first while bringing Sokolova’s killer to justice by “lifting” a fingerprint from a mobile phone video. They spotted a recognisable print in a film showing Viktorija’s murderer scrolling through his iPhone for passwords as he prepared to delete evidence linking him to the schoolgirl. The footage did not show the boy’s face, meaning a fingerprint was the only means of proving he was using the phone.

The boy, who refused to give evidence and claimed to have learning difficulties, initially denied meeting Viktorija.

He later told police that his Facebook account had been hacked, before changing his story and claiming consensual sex had taken place in the park, where he had left Viktorija unharmed.

Opening the case against the boy at the start of the trial, Jonathan Rees QC, prosecuting, said Viktorija’s partially clothed body was found by a dog-walker at about 7am on 12 April.

Rees told the jury: “The postmortem examination of her body revealed that she had been subjected to a sustained and ferocious attack to the head, which involved a minimum of 21 blows.

“The force of the attack was such that it caused multiple fractures of the underlying skullcap and her facial skeleton. In short, to put it into lay-person’s terms, her head had been smashed in.”

The trial was told that Viktorija had a turbulent relationship with her parents. She had been reported to police as a missing person in the months before her death after spending nights away from home and staying with friends.

CCTV evidence presented at the trial showed the boy was carrying a backpack and changed his trousers while in the park between 10.44pm on 11 April and 12.44am on 12 April.

Dete Insp Caroline Corfield said: “The impact on Viktorija’s family has been huge. It’s impossible to imagine what it is like to learn of the murder of your child, then to hear the horrific details of that murder, which are inescapable because they have to be presented in court.

“But in this particular case the defence pointed the finger of blame very specifically at Viktorija’s parents. They were asked in court whether they had murdered Viktorija.”

Corfield said Viktorija’s mother, Karolina Valantiniene, and her stepfather, Saidas Valantinas, who had reported her missing, were eliminated from the inquiry at an early stage using CCTV footage.

The couple were called to give evidence after jurors heard that microscopic traces of Valantinas’ semen had been found on Viktorija’s underwear, believed to be the result of innocent transfer from clothing to clothing.

The defendant, who was cleared of sexual penetration of a corpse, faces an automatic life sentence when he is sentenced on 22 February.

Adjourning the case for psychiatric reports, Mr Justice Jeremy Baker told the boy: “As has been explained to you there is only one sentence which can be imposed upon you.

“However, I do have to consider the appropriate minimum term that you will have to serve, and for that purpose I am going to ask for various pieces of information about you.”