Joseph Trevor murdered Megan Newton, 18, at her flat in Stoke-on-Trent last April after she’d kindly offered him a place to sleep.
Trevor, 19, who was jailed for a minimum 22 years on Monday, had told her he didn’t want to go home because he had been drinking and taking drugs.
CCTV footage showed Trevor, the son of a retired police officer, accompanying Miss Newton into her bedsit after the old school friends had bumped into each at a nightclub.
Just over two hours later, he’s seen in security footage walking away from Miss Newton’s flat and staring at his right hand, which was covered in blood.
Earlier CCTV showed her letting him into her flat, where she had offered him a place to stay.
Once inside, Trevor raped her, strangled her and stabbed her at least nine times using a knife from her kitchen. He then let himself out of her building complex using her key, which he tossed in a car park.
The pair, who knew each other from school, had bumped into each other at a nightclub earlier in the evening.
The court heard that police had detained Trevor and seized a bag of ketamine from him earlier in the night before releasing him, because he was “unfit” for interview.
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When the nightclub closed, Miss Newton and Trevor, described in court as “passing friends” at school, found themselves at the same taxi rank.
Trevor, telling friends his parents “would go mad” if he arrived home in his drunken state, was trying to find a place to sleep for the night, and she told him he could stay in her flat.
The court heard an allegation of oral rape was made against Trevor when he was aged 15 but never prosecuted.
Sports coach Miss Newton had been planning to go to university to become a sports therapist, with hopes of a scholarship in the US.
Read more: Murdered football coach Megan Newton ‘had everything to live for’
Judge Michael Chambers QC said: “This remains a brutal and sustained attack committed in a most callous way in her own home.
“Megan Newton had her whole life before her. She had all the hopes and dreams of an 18-year-old.”
Senior investigating officer, Detective Inspector Cheryl Hannan, of Staffordshire Police, said: “Trevor carried out a sustained and violent assault on Megan.
“She had kindly offered him a place to stay overnight because he had taken drugs and had been stopped by police and was worried about returning home.
“In return he attacked and killed her and left her lying in her own bed while he let himself out and told no one what he had done.”
In a statement, Miss Newton’s family said: “The loss of Meg is unbearable. We’re heartbroken and will always remain so.”