Within 24 hours of the murder of Brianna Ghey, investigating officers had identified the suspects – two teenagers who thought that hiding the most brutal of killings would be easy.
The pair, who were just 15 at the time, were quickly arrested at their homes and taken away for questioning.
Detectives would soon unravel the crime despite the killers arrogantly presuming their endless lies would save them.
Sixteen-year-old Brianna, who was transgender, was stabbed 28 times in broad daylight in Culcheth Linear Park in Cheshire on the afternoon of 11 February.
The teenagers, who were referred to only as girl X and boy Y during their trial due to their age, have both been convicted of her murder.
Warning: Some readers might find the following report distressing
The court heard how their web of deceit began shortly after the killing when the pair began to craft what they thought would emerge to be a subtle cover story.
Girl X messaged boy Y to say a “woman got stabbed” in the park.
“Holy crap” was boy X’s reply despite the pair later admitting to police they were present during the stabbing – albeit blaming each other for the killing.
The following day, girl X messaged Brianna saying: “Girl, is everything okay? Some teenage girl got killed in Linear Park its on news everywhere.
“And why did you ditch us for some random man from Manchester. Like wtf.”
For Det Ch Supt Mike Evans, it became clear early on that the two school pupils believed they could cover their tracks.
Girl X, who has traits of autism and ADHD, even assured boy Y, who has been diagnosed with selective mutism and autism spectrum disorder, that he would not be caught, criticising the capabilities of police in the area.
“These are really high functioning, intelligent children,” said the officer, who is head of crime at Cheshire Police.
“I know people sat at home reading this will have this sort of image that they’ve built themselves.
“But actually they’re both really clever kids and very bright, very articulate.
“I think probably their downfall has been their confidence or arrogance around the fact that they thought that they could take another human life and then thought there would be no comeuppance for them and they’d never get caught.”
Once their lies unravelled, the truth that emerged was that both had a fascination with violence, torture and murder and had planned the killing for weeks.
Messages between them showed they encouraged one and other to think about how they would actually carry out a killing.
Girl X admitted she enjoyed “dark fantasies” but the jury did not accept her claims that she had no intention of turning them into reality.
Neither did the jury accept boy Y’s claims that he had simply played along with these fantasies and did not take them seriously.
However, police admit they may never know exactly what motivated the teenagers to act.
Det Ch Supt Mike Evans described the attack on Brianna as “violent and vicious”
Det Ch Supt Evans continued: “I don’t think many of us has ever seen the level of depravity shown and the dehumanising nature of the text messages between the two, and the hatred towards Brianna and others for no reason whatsoever.
“And just that thirst for killing from two 15 year olds – that was really disturbing.
“And we still do not know to why they’ve done it. What led them to want to do it?
“Obviously now they they’ve played on the fact that they thought it was fantasy and but when you read those messages, it was quite clear that was a plan. That wasn’t a fantasy.”
Brianna was found by dog walkers in Culcheth Linear Park
Both teenagers spoke about people they wanted to kill and by 26 January – just two weeks before Brianna’s death – they had compiled a “kill list” of five people.
“We never built this case around a transgender element,” he said.
“This was about the murder of a young, vulnerable girl. We obviously know there was that kill list, which had five people on it. Brianna was one of them.
“Brianna was the only person on that list who was transgender. This was about murderous intent for somebody.”
In one message, girl X messaged boy Y telling him she was “obsessed over someone” called Brianna but did not have feelings for the teenager.
“She was really cruel. This girl was the one who has befriended and who has betrayed and who has essentially instigated this attack throughout,” said Det Ch Supt Evans.
“She has been the planner behind it. She’s been the person who was sending the text messages and ultimately lured Brianna out to her death and then murdered her in the coldest fashion.”
Ursula Doyle, the Crown Prosecution Service’s deputy chief crown prosecutor, said one of the key elements of the case was the messages, which “provided a terrifying insight into the warped fantasies” of the teenagers.
“This actually gave us detailed knowledge and insight into the relationship of the two defendants, what they talked about, the dark fantasies and the content of those messages were chilling,” she added.
“It also gave us the evidence to actually see how the whole event had unfolded from the planning right the way through to luring Brianna to the park on that date.
“In fact, the way the attack was carried out was exactly the way it had been planned.”
A handwritten note of “murder plan” to kill Brianna was found in girl X’s bedroom
She said the investigation was one of the most disturbing cases she had dealt with during her career.
“The planning, the violence and the age of the killers is beyond belief,” she said.
Det Ch Supt Evans added: “I think this case is truly horrific.
“I would rather we talked about Brianna than these two individuals.
“I think what they did on that day and leading up to that day was evil. It was cruel and it was vicious.
“But as I say, I only want to think about Brianna going forward, not these two individuals who hopefully now will remain in prison for a considerable amount of time.”
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