One of the two teenagers convicted of the murder of 16-year-old Brianna Ghey has failed in his attempt to reduce the length of his sentence after claiming a judge failed to take into account his “immaturity”.

Eddie Ratcliffe was detained for life with a minimum term of 20 years in February for the murder, along with Scarlett Jenkinson, who received a minimum term of 22 years.

Brianna was stabbed 28 times with a hunting knife during the “exceptionally brutal” attack in Linear Park, Culcheth, near Warrington, in February last year.

Ratcliffe, who was 15 at the time of the killing and is now 17, was also found to have been transphobic about his victim. He was seeking leave to appeal against his sentence but had the bid rejected at the court of appeal on Thursday.

At a hearing on Thursday, lawyers for Ratcliffe, who has been diagnosed with autism spectrum disorder and selective mutism, said the judge failed to “sufficiently” take into account his age and maturity when deciding his sentence.

Speaking at the court in London, Richard Littler KC, for Ratcliffe, said: “It is culpability and maturity which are at the heart of this application.”

“It is right to say that on any analysis of the applicant’s maturity, he is closer to the starting point of a 14-year-old rather than a 17-year-old boy,” he said. “The point we make is age and maturity were very important issues in this case, and could very much affect the end result for this particular applicant.”

Littler said Ratcliffe was found to have “poor social skills” and “immaturity” as well as “a lower-than-expected ability to express what he thinks or articulate his ideas”, adding that the sentence was “far too high”.

He said: “There is no doubt they were taken into account, but they were not taken into account fully.”

Ratcliffe was attending the hearing via video link, with his mother present in court. The court was told that Brianna’s family were also in attendance remotely.

The Crown Prosecution Service opposed the appeal attempt. In a ruling on Thursday, three senior judges dismissed it, finding that arguments made in favour of reducing Ratcliffe’s sentence were “based on a false premise”.

Summarising their judgment, the lady chief justice, Baroness Carr, sitting with Mr Justice Lavender and Mr Justice Murray, said: “The sentence imposed by the judge on the applicant was neither manifestly excessive, nor wrong in principle. The proposed grounds (of appeal) are not arguable.”

The earlier trial at Manchester crown court heard that Brianna had thousands of followers on TikTok, but in reality was a withdrawn, shy and anxious teenager who struggled with depression and rarely left home.

Jurors were told that the two killers were intelligent, “high-functioning” and came from normal backgrounds, but had a fascination for violence, torture and murder and a “thirst for killing”.

Jenkinson, who lived close to the park in Culcheth, had been asked to leave her school, Culcheth High, over giving cannabis-laced gummy sweets to another pupil and joined Brianna’s school, Birchwood High, in October 2022.

She quickly became “obsessed” with Brianna, and along with Ratcliffe drew up a “kill list” of four other youths they wanted to harm until Brianna had the “misfortune” to be befriended by Jenkinson.

The pair discussed the murder for weeks, detailed in Jenkinson’s handwritten murder plan and phone messages found by detectives. Jenkinson also told Ratcliffe she wanted to stab Brianna “jus coz its fun lol … I want to see the pure horror on her face and hear her scream”.

They lured Brianna to Linear Park on 11 February last year where she was attacked with Ratcliffe’s hunting knife, which had a 13cm blade. She was stabbed in the head, neck, chest and back, with Jenkinson deleting a Snapchat conversation between them and inventing a cover story.

Both teenagers were arrested an hour later, with the murder weapon and blood-stained clothing found in Ratcliffe’s bedroom.