Jamie Reynolds, 23, was arrested in Glasgow in May following a UK-wide manhunt which was launched after the killing of Georgia Williams in their home town of Wellington, Shropshire.
Reynolds, who pled guilty to the murder yesterday, was captured on CCTV cameras in the high-rise car park of a hotel in the city centre shortly before his arrest on May 29, three days after his victim was reported missing.
He sat with his head bowed in the dock after entering a guilty plea yesterday at Stafford Crown Court plea on what was scheduled to be the first day of a three-week trial.
Georgia, a member of the Air Training Corps who planned to join the RAF as a paramedic, knew Reynolds and is believed to have been killed at an address in Wellington.
The teenager's body was found around 50 miles away, off the Nant-y-Garth pass.
Reynolds, who will be sentenced later this month, is known to have killed Georgia after inviting her to pose for a photo shoot.
His victim, who had previously done modelling work to help her sister's business, is believed to have died on the day she was reported missing.
Before Reynolds was arrested, media reports claimed he had made advances via Facebook and other social media sites towards Georgia, a former head girl at Telford's Ercall Wood Technology College.
Friends said the A-level student, who was just 5ft 3ins and of slim build, had made it clear she was not interested in a relationship with Reynolds.
Although the facts of the case were not opened at today's hearing, prosecutor David Crigman, QC, told Mr Justice Wilkie he would have to view distressing photographic material relevant to the case before passing sentence.
Further material relating to pictures posted online by other "innocent girls" and examples of extreme pornography also form part of the evidence against Reynolds, Mr Crigman told the court.
The barrister said: "The material in question is photographic material relevant to the moments before and after the murder took place."
Mr Justice Wilkie remanded Reynolds in custody until December 19 pending further psychiatric reports.
The judge said the case was one in which he would have to consider whether a whole life term was appropriate.
At the time of Reynolds's arrest, detectives said a van he was driving was known to have been in the Wrexham area at about 5.30pm on May 27 and was seen in Cheshire heading north five hours later.
Georgia's parents and her sister Scarlett were in court to see Reynolds admit his guilt.
In a statement issued on behalf of the family, her father Steve Williams, a detective constable with West Mercia Police, said: "The pain we feel is as raw now as it was when our beautiful Georgia was taken from us back in May.
"We will never ever be able to make any sense of what happened, or why it happened to a young woman as caring, kind and generous as our Georgia.
"Today's guilty plea gives us no satisfaction at all; we do not and will never understand the heartbreaking events of earlier this year that changed our lives for ever."
Superintendent Adrian McGee, who helped to oversee the murder inquiry, confirmed that Georgia was killed at Reynolds' home address.
Speaking outside the court, Mr McGee said: "It is important that Mr Reynolds pleaded guilty as this at least saves Georgia's family the further trauma of a full trial.
"We know the plea does nothing to ease their pain but hopefully it will help them begin to move forward with their lives once sentence is passed."