Two youths who deny the frenzied murder of transgender teenager Brianna Ghey cannot both be telling the truth, a court heard.

Brianna, 16, was stabbed with a hunting knife 28 times in her head, neck, chest and back in Linear Park, Culcheth, a village near Warrington, Cheshire, on the afternoon of February 11.

Two teenagers, identified only as girl X and boy Y, both now aged 16 but 15 at the time, deny murder and are blaming each other for Brianna’s death.

Both say their backs were turned when the other defendant began stabbing Brianna.

On the facts of the case and the evidence before you, they can’t both be telling the truth

Trial judge Mrs Justice Yip, on day 15 of the trial, told the jury on Friday: “On the facts of the case and the evidence before you, they can’t both be telling the truth.”

Giving legal directions to jurors after the prosecution and defence case concluded, she added: “The defendants are each charged with Brianna Ghey’s murder. The prosecution case is that they acted together to bring about her death and both intending that she should be killed.

“Each defendant says that the other defendant is the person who stabbed Brianna and was not expecting or wanting Brianna to be killed.

“You should approach the evidence calmly and dispassionately. You must not be influenced by any emotional reaction or sympathy for anyone involved.”

The trial has heard both defendants had a fascination for violence, torture and murder and had planned the killing for weeks, it is alleged.

Jurors heard girl X enjoyed watching internet torture and killing material from the “dark web” and had an interest in serial killers.

And the jury was shown an alleged “murder plan” on how to kill Brianna along with phone messages they exchanged, including a “kill list” of other children they planned to harm.

Girl X has said she enjoyed “dark fantasies” but with no intention to ever turn them into reality, while boy Y said he went along with them and did not take them seriously; both say they never expected the other to act on them.

The judge told jurors that next week prosecution and defence counsel will give closing speeches and she will sum up the evidence before they retire to consider verdicts.

The trial was adjourned until Monday.