It's a murder that has remained unsolved for decades.
But with the 35th anniversary of the killing of Lisa Hession, 14, falling this weekend, the M.E.N., can reveal what it will take to catch him.
Quite simply, police already have DNA.
And they believe the killer had links to Leigh, where Lisa lived and died.
All they need is a name that matches the sample.
The people of Leigh have shown a determination to lift the shadow of the unsolved case, ringing police, after each new appeal, with tip-offs.
But the right person hasn't yet been identified.
And, incredibly, whoever killed Lisa appears not to have offended in the decades since.
DNA technology has advanced to the point where they could identify the culprit even if a blood relative of theirs was arrested.
But that hasn't happened either.
And until it does police are dependent on the continued efforts of the people of Leigh in coming forward with information.
While they wait, Martin Bottomley, Head of the Cold Case Unit, has given the M.E.N. a new insight into what his team know.
The M.E.N. also looks at how other cases, which might have seemed like lost hopes, have been cracked by his team using DNA.
We meet the volunteers in Lisa's hometown who have made it their mission to get justice for the murdered schoolgirl.
And we retrace Lisa's last steps - because it may just trigger a memory that proves essential.
Lisa's tragic last walk
The schoolgirl was walking back from a party in Leigh when she was attacked.
Her mum, Christine, had allowed her to go as long as she was back home by 10.30pm.
She kissed her boyfriend, then 16, goodbye at the gate at 10.15pm.
She walked two miles through the town centre and onto St Helens Road, before she was seen turning into Buck Street.
At that point she was a minute walk, just a hundred yards, from the front door of her home on Bonnywell Road.
A man walking his dog with his 13-year-old son found Lisa's body in a ginnel behind Rugby Road, at five minutes before midnight on Saturday December 8th 1984.
In a sexually motivated attack the killer gripped her striped T-shirt around her neck with one hand and clamped his other hand over her mouth.
An asthmatic, Lisa died from asphyxia.
The school disco which Lisa had prepared for, with a glamorous new look of gold and blonde highlights in her hair, was cancelled out of respect for her family.
Police have arrested only one person on suspicion of the killing.
He died in 2005, having been ruled out.
In January 2017 Lisa's mother Christine died, aged 69, after a short battle with cancer, without seeing justice for her daughter.
And so a £50,000 reward for information remains unclaimed.
The key to the case
GMP's Cold Case Unit has the key to identifying the killer in their possession.
A forensic sample was recovered from Lisa's body - and that would go on to yield a partial DNA sample, years later, when the technology had developed.
Martin Bottomley, Head of the Cold Case Unit, this week told the M.E.N: "It would be good enough for direct comparison, once we have a name.
"I think the mechanics of the incident tend to suggest the man who did this would have good local knowledge.
"We have made many appeals over the years regarding Lisa's murder and we always get a good response.
"We have followed up numerous lines of inquiry after the public have suggested names.
"The case is still remembered by a lot of local people who still care.
"This case will never be closed and we are determined to get justice for Lisa's family even though her mother has now died."
In the four months before Lisa's death a man attacked three other girls in the same area of Leigh. In each case sex was the motive.
And, five months after Lisa's murder, a woman was attacked close to the ginnel where Lisa's body was found.
An E-fit of a 'baby-faced' man of 20, believed to be responsible for the three attacks before Lisa was killed, was issued by police in January 1985.
He has never been identified.
The potential value of the forensic sample recovered from Lisa's body became apparent two years after she was killed - after a crime, with chilling echoes of her murder, over 100 miles away.
In the summer of 1986 a 15-year-old girl, Dawn Ashworth, left a friend's house in the Leicestershire village of Narborough.
She lived in the nearby village of Enderby, a few minutes walk away.
Dawn took a short cut along a footpath - and then vanished.
Two days later her body was found in a nearby field covered in branches. She had been raped and strangled.
The case paralysed the local community with fear.
Police suspected a local lad with learning difficulties, and after the 17-year-old was arrested he confessed.
Two and a half years earlier another 15-year-old, Lynda Mann, had been murdered a few hundred yards from the scene of Dawn's murder.
Police suspected the teenager of both - until DNA fingerprinting, then a science in its infancy, pointed in a completely different direction.
After seeing an article in the Leicester Mercury a detective contacted geneticist Alec Jeffreys at Leicester University, thinking it could help him prove the boy had done both murders.
Jeffreys was able to prove the same person was responsible - but it wasn't the teenager.
The youth was set free and police then decided to try and use the new technology to their advantage.
They decided to screen every man who lived in the area.
After eight months 5,500 men had given blood samples - but there was no match.
Then, a conversation in a local pub was overheard.
A man was having a pint with friends in Leicester and confessed that he had he had impersonated a local man, Colin Pitchfork, in order to take the blood test on his behalf.
Pitchfork, a married man with two children, admitted killing and raping both girls and was jailed for life in 1988.
It was the first time DNA fingerprinting was used in a criminal investigation - and Pitchfork became the first person in the world to be convicted of murder on the basis of DNA.
How justice has caught up with Manchester's guilty after decades
The circumstances of Lisa's murder point towards the killer having local knowledge.
When he ghosted behind her, he knew that at the end of Buck Street was the alleyway where he would bundle her - out of sight and earshot of neighbours.
A keen cross country runner, who had run for Leigh Harriers, Lisa was wearing a three-quarter length navy coat, white skirt, T-shirt, red jumper and white canvas boots.
Detective Rita Kraft would later wear similar clothing and follow the route of Lisa’s last walk in a bid to find new witnesses.
In 2011, using the partial DNA sample, GMP carried out a mass swabbing of men in Leigh and Wigan - just as had been done in the Pitchfork case.
But as it didn't identify Lisa's killer, a reasonable assumption is that he is either dead, or now lives elsewhere and has never been in trouble since.
But that doesn't mean that there isn't a clue to his identity out there that could be matched with the DNA sample.
Indeed, if he is alive - he may still be caught due to the DNA of his relatives and advances in technology.
In 2013 a dad who had raped a woman 24 years earlier was jailed, following a GMP Cold Case investigation, after he was found to be related to someone on the system.
Barry Howell was separated from his first wife and 'angry at women' when he raped the 25-year-old woman and threatened to stab and kill her at Red Bank, near Victoria Station, back in November 1989.
The victim was unable to identify him because he pounced from behind, but police were able to recover a forensic sample from her.
Howell evaded justice for over two decades because he committed no other offences before or after, and technology hadn't advanced far enough to identify the sample.
But his secret finally caught up with him when Cold Case detectives ran the sample through the national DNA database and identified him by establishing that he was related to someone whose DNA was on the system in entirely unconnected circumstances.
Howell was jailed for nine years.
Then, in 2016, another rapist, who had got away with his crime for more than 30 years, was brought to justice after a DNA breakthrough.
In 1984, Henry Drennan broke into the Manchester home of a young mum whose husband had just left for work.
He clamped his hand over her mouth and raped her, holding a pair of scissors to her face, as her young child slept in the next room.
At the time Drennan was a prolific prowler and sex criminal living in Oldham.
But he was not linked to the attack in north Manchester until police launched a cold case review in 2015 and used the latest DNA technology to decode an old sample.
He had been living over 200 miles away, in North Lanarkshire, just outside Glasgow, at the time. He was jailed for ten years.
The people who won't let Lisa be forgotten
Andrea Ashcroft Aldred, who knew Lisa, and Ryan Daly have set up the social media group Let's get justice for Lisa Jane Hession and her mum Christine .
Andrea said: "Lisa is always on my mind at this time of year, as I start to think about Christmas, my family, my daughters and grandchildren.
"It makes me think of Christine and her heartache, her never becoming a nana or seeing Lisa marry or becoming a mother and then I think of Lisa and how much life she had snatched away.
"It really isn't fair that (the killer) has walked and lived life for 35 years, probably got children, may have been married possibly his mother having what Christine didn't."
Ryan added: "With it being 35 years since this horrific case happened, I really hope this person who is responsible is caught.
"Whether he is alive or dead, it would be some solace for Lisa's family and friends if this case could finally be solved.
"I hope it is.
"When I started the campaign in October 2016, it was to raise awareness, as I thought it was tragic that Lisa’s Mum passed away, without ever getting closure.
"So Andrea and I decided to raise awareness about the case, and especially because it happened in our hometown, and Lisa was also Andrea’s friend.
"Another reason we continued the campaign on social media, was when The BBC axed Crimewatch, in October 2017.
"I really hope even after these years, there is a breakthrough.
"We’re shocked that no one has been named by now especially after the £50,000 reward was offered in December 2017.
"However, in my opinion if people think they know something no matter how small, they should not have to be offered money to speak up."
In 2014, three years before she died, Lisa's mum, Christine, said: "It's always there at the back of your mind, knowing that nobody has paid for what they have done to your child.
"They may be married or have children of their own, living a good life.
"I don't know, but they have not paid for what they have done and if no one comes forward they never will."
Cold case officers hope, that even if no one comes forward, one day, thanks to science, they will knock on the killer's door.
Anyone with information can call GMP's Cold Case Unit on 0161 856 5978 or Crimestoppers on 0800 555 111.