Outwardly described by detectives as appearing to be “a normal kid from a normal family”, Jenkinson kept secret notes on her dark fantasies of death, torture, murder and serial killers in notebooks in her bedroom at the family home she shared with her parents, both teachers, and three older brothers.

Detectives say her “thirst for killing” grew over time, shared with Ratcliffe, neither blindly leading the other, both hand in hand down a path getting more extreme and more real, in a “cocoon world they alone inhabited”, their trial heard.

Jenkinson told him she was a “satanist” and had a particular interest in serial killers Richard Ramirez, dubbed the Night Stalker, and cannibal Jeffrey Dahmer.

Unsuspecting Brianna entered this world when Jenkinson, by then 15, transferred to her school, Birchwood High, in November 2022.

After striking up a conversation about eyeliner the two became friends, hanging out in the school inclusion unit and outside class on WhatsApp and Instagram.

Brianna, despite her appearance and having thousands of followers on TikTok, was in truth, vulnerable, nervous and anxious, with few friends and who rarely left home.

Jenkinson and Ratcliffe drew up a “kill list” of five people they deemed worthy of murder over insignificant or minor dislikes.

But Brianna represented an easy kill.

Jenkinson told Ratcliffe people knew Brianna was depressed and anxious and first tried to murder her with an overdose of tablets.

When it failed Jenkinson then persuaded Brianna to leave home in Birchwood and meet her and Ratcliffe on a Saturday afternoon at Linear Park in Culcheth – just round the corner from her home.

She wanted to stab Brianna “jus coz its fun lol… I want to see the pure horror on her face and hear her scream”, she told Ratcliffe.

Jenkinson told Brianna to get a single not a return bus ticket to Culcheth – and reminded Ratcliffe to bring his knife.

They had already staked out a hidden spot in the woods, talked about a distraction tactic and how they would stab their victim.

At some point Jenkinson took a final photo of Brianna, the friend she was about to murder.

Shortly after 3pm, Brianna sitting on a bench, was suddenly attacked with Ratcliffe’s hunting knife. She was stabbed 28 times in the head, neck, back and chest and never stood a chance.

Seconds later Jenkinson had the presence of mind to delete Snapchat conversations with Brianna.

Then she went home and played video games – Ark, No Man’s Sky and Minecraft – exchanging jokey texts with Ratcliffe.

She soon invented a cover story that her friend had left her and Ratcliffe at the park and gone off with another youth.

And she arrogantly told Ratcliffe not to worry about getting caught as the local police were, “shite”.

She claimed she burst out crying when she found out Brianna was dead and ran to her mother in tears.

And she posted a ‘rest in peace’ photo tribute on Snapchat, saying: “Brianna was one of the best people I have ever met and such an amazing friend its so f****** sickening what got done to her.”

An hour later she was under arrest.

Her phone seized and home searched, detectives found incriminating evidence.

On one page from her notebook, found crumpled up on the floor of her bedroom, was a handwritten note titled ‘The Murder Plan’ Victim: Brianna Ghey, giving the exact date and details of the murder they had planned and carried out the day before.

A love heart and smiley face had been doodled on the top corner of the page.

Under arrest, she laughed 17 times during her lying account to police detectives. “I’m good at hiding stuff and playing the victim,” she had told Ratcliffe.

Awaiting trial she was diagnosed as having mildly autistic traits and traits of ADHD.

But in the glare of the courtroom she felt “overwhelmed” after the first day of her trial and left visibly shaking, sometimes dabbing her eyes with a tissue.

And the twitch to the right side of her face and right eye would become more pronounced under stress as her story fell apart in the witness box.