A 23-year-old man killed teenager Georgia Williams after luring her to his parents' house and hanging her, a court has heard.
Jamie Reynolds was a "a sexual deviant", "a manipulative and conning individual who operated in denial" and had "a morbid fascination" in extreme pornography depicting violence against women, prosecutor David Crigman QC said.
Reynolds pleaded guilty earlier this month to murdering 17-year-old Georgia in May, on what was scheduled to be the first day of his trial at Stafford Crown Court.
At the start of a two-day prosecution and sentencing hearing at the court today, Mr Crigman said that at the time of his arrest for murder, Reynolds had 16,800 images and 72 videos of extreme pornography on his computer, including digitally-doctored images of up to eight other women he personally knew in which ropes had been added around their necks.
He had written 40 graphic short stories, which featured a fatal assault on a woman, "followed by acts of sexual violation".
It also emerged that Reynolds had written a "script" in which he described in detail entrapping and killing a victim.
Mr Crigman said, in regards to murdering Georgia, Reynolds followed "a good deal of his pre-written script".
Members of her family sat and listened in silence as Mr Crigman said it was "a wholly deliberate act of motivation" that Reynolds wanted to watch his victim die, partly through his interest of "a voyeur" and partly for sexual reasons.
Mr Crigman added that, following death, it was then Reynolds' intent "to engage in sexual activity with her body".
He said: "In life she (Georgia) would never have engaged in any sex activity with this defendant.
"They were friends and she made it clear she had no romantic interest in him."
Mr Crigman said Reynolds carried out a "scripted, sadistic and sexually-motivated murder", and planned the killing meticulously.
Georgia, a member of the Air Training Corps who planned to join the RAF as a paramedic, is said by the prosecution to have been murdered at Reynolds' home in Avondale Road, Wellington, in Shropshire, on Sunday May 26.
As Mr Crigman continued to set out the case, Reynolds sat in the dock wearing a two-piece suit, purple shirt and tie, looking down and fiddling with his hands in his lap.
Earlier in the year, Reynolds had texted and messaged Miss Williams over social media setting out his romantic attachment to her.
Mr Crigman set out a series of messages Reynolds wrote and in one he told her: "I want to be with you, you're a stunning young woman.
"I enjoy your company, you make me laugh."
By late February he was still texting her despite Miss Williams' efforts to let him down gently, Mr Crigman said.
He messaged her saying: "I don't know why I'm still interested - damn you 'ginge'."
She replied "I am kind of seeing someone. I don't see you in that way. Just stop, I don't want to ruin our friendship."
She added: "I told you last time, I just wanted to be friends."
Reynolds responded saying he felt like a mug, and barraged her with texts, however she did not respond.
Miss Williams was not the only target of Reynolds' affections during the period earlier this year, with the former shop worker also messaging other girls he knew with red hair, inviting them around for a photoshoot at his home.
Mr Crigman said Reynolds had extended this same invitation to Miss Williams, feigning an interest in developing a career in photography, while plotting murder.
He had bought items to engineer what Mr Crigman referred to as "a hanging mechanism" including a length of rope which he had learned to tie into a hangman's noose which was then fitted to the loft hatch above the landing, in his parents' house.