A boy accused of the frenzied stabbing of a transgender teenager was merely an “extra” in a murder choreographed by his co-accused, a court has heard.

Brianna Ghey, 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, with each blaming the other for the killing.

Both say their backs were turned when the other suddenly began stabbing Brianna, jurors at Manchester Crown Court have been told.

The defendants had a fascination with violence, torture and murder and had planned the killing for weeks, it is alleged, and both were “in it together from first to last”, Deanna Heer KC, prosecuting, told the jury in her closing speech.

On day 17 of the trial in his closing speech, Richard Littler KC, defending boy Y, suggested the socially awkward youth, diagnosed with autism spectrum disorder and selective mutism, was controlled and manipulated by girl X.

Boy Y told jurors he “admired the craftsmanship” of his knife and brought it to the park to show to girl X. He had been “admiring trees” in the park, then, while relieving himself behind a tree, girl X stabbed Brianna before handing him back the knife.

If this case was a play, it would definitely be a tragedy. The script would be written by girl X, directed by X, stage-managed by X, produced by X, and the central character would have to be X

The knife was found in his bedroom along with clothes also stained with Brianna’s blood.

Mr Littler said: “If this case was a play, it would definitely be a tragedy.

“The script would be written by girl X, directed by X, stage-managed by X, produced by X, and the central character would have to be X.

“The central issue in the case is whether you can be sure whether Boy Y was part of the cast or just an extra drafted in for that afternoon on February 11 in Culcheth.

“Was he a fully paid up member of the plan?”

Mr Littler asked jurors to concentrate on the evidence and not “emotive motives”, and said no-one should discriminate against anyone because of gender identity or neuro-diversity.

He said: “We don’t mock an individual for how they look or behave. And if someone enjoys admiring trees or admiring the craftsmanship of a knife that his dad bought for him on holiday, well, that’s OK. Autism.”

Brianna’s blood on Y’s clothing but not on X’s did not mean he was the killer, Mr Littler suggested. He said it showed she is “criminally minded” and may have washed her clothes before police seized them.

Earlier, jurors were told girl X enjoyed “dark fantasies” about killing and torture, 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 said they never expected the other to act on them.

Mr Littler continued: “His defence has always been that what happened in the Culcheth park, he did not expect it to happen.

“When he handed the knife over, he did not believe for one moment this was going to be used.

“He believed she was a fantasist. He went along with her stories.

“She did turn her fantasy into reality.

“That’s why she wrote the play, she directed it, she produced it, she stage-managed it.

“Boy Y was an extra. He did not stab her.”

Trial judge Mrs Justice Yip has told the jury they will retire to consider their verdicts on Wednesday morning.