Each unsolved murder leaves a trail of unanswered questions. From the obvious - who did it and why? - to the obscure.

Among the cases in Greater Manchester Police's files are those that feature details that remain shrouded in mystery.

Who was the person last seen with the victim? What was the meaning of the unknown killer's ritual?

What secret was troubling the victim before their death? Why might a particular item be missing from the scene? Why might people who know something appear reluctant to talk?

Here, as GMP's Cold Cases detectives renew their appeal for information, the M.E.N. revisits the unanswered questions in five unsolved murders - and one double murder - in which the killer has yet to face justice.

The missing scarf and the mystery witnesses

(Image: Dominic Salter)

Bolton, November 16, 1940.

Minnie Stott went out into a November night in colour; a woolen coat, in striking blue, a tweed skirt of green, flesh-coloured stockings, brown shoes. Around her neck she wore a scarf in a deep green crepe de chine.

Britain had been at war for over a year, but dancing was an escape from the gloom. Minnie, 17, took lessons at Aspin Hall, and was a regular at the Palais de Danse.

She was well-known in Bolton, where she lived and worked as the manageress of a grocery shop.

But, after she was found dead, few would help the police. Why?

That evening an adventure movie was showing - Bulldog Drummond at Bay - at Queen's cinema.

Minnie finished work at 6.40pm, and mentioned going to the pictures to her dad when she left the family home at Clarence Street, near the town centre.

At 8pm, 15 minutes after she left the house, she called into the United Cow Products restaurant where her mother waited tables - serving up dishes of tripe, cowheel and ox tail to customers.

Three-and-a-half hours later, while making routine checks, PC Harry C Brooks finds Minnie. There's still a 'faint warmth' when the officer touches her face.

She lies on her back in the yard of Parker's Garage, near Bradshawgate, her right arm partly extended over her head, a trickle of blood from her mouth, and a red weal on her neck.

It's 11.53pm and she's probably been dead for two hours.

Her handbag is by her feet, with nothing taken. But her scarf and her white Vedonis knickers are missing.

She has been strangled.

That Saturday night in Bolton would have been teeming with people. Others on a night out, soldiers and airmen passing through; but when police appeal for information, showing the clothes she had been wearing on screens in the cinemas, no-one comes forward.

No-one seems to know, or wants to say, where Minnie went after she left the UCP. Police find out she had a drink with a soldier, a couple of days before, but he is very quickly ruled out as a suspect.

Eventually, a woman who has a sweet shop says Minnie and another girl came into her shop at 8.20pm on November 16. Minnie bought sweets - which had been recovered from her handbag - and the other girl bought cigarettes.

That girl never came forward either, despite a police appeal.

Minnie has been dead for nearly two months by the time someone admits to having seen her after that.

Her parents are visiting her grave, on January 12, when a woman, never identified, tells them that Minnie had been with two other girls in Bradshawgate on the night she died. She says they were followed by two men - one of whom she named - before Minnie got into a car with them.

The other two girls, who were said to have run off, were never traced. The two men were never found. Neither was the scarf that Minnie had had around her neck when she left the house.

(Image: Dominic Salter)

Nearly 70 years on, a possible explanation for the slience around Minnie's appalling death emerges.

This was the time of The Blitz - when the shadow of death hung over the country. Some historians now see this period as one when sexual attitudes relaxed - even if the culture of secrecy and public shame around sex outside marriage hadn't.

Local historian David Hargreaves, who spent years researching Minnie's case, told the M.E.N. in 2016 that she may have been involved in sex work.

If so, it may be that the desire of Minnie's friends to protect her reputation, and their own, protected a killer.

What was worrying Joe?

To his little sister Margaret, Joe Gallagher was a rock star.

By the age of 30 he has served in the army, lived in a commune near Glastonbury, worked as a roadie for a band, and been married and estranged from his wife.

He rides a Triumph Tiger and a Norton Commando and has friends in the Dragons North West chapter of the Hells Angels.

A former pupil of St Bede's College, he excelled academically before embracing the counterculture of the 1970s. He lived in Hyde, with his girlfriend Frieda, at Hallbottom Road in Hyde, and worked as a taxi driver.

"I absolutely adored him", Margaret Linnane, Joe's sister told the M.E.N. "He left home when I was three. We didn’t get to see him that often. He would just breeze in like a whirlwind, arriving on his motorbike.

“He was almost like a rock star to me - I just adored him. He was exciting, and he was clever.”

(Image: manchester Evening News)

Frieda Hunter, Joe's girlfriend had originally moved to Tameside from Scotland to study creative arts at a local college. She dropped out of the course but stayed in the area.

In February, 1979, she has just started work as a barmaid at the Queens Hotel in Hyde.

“I got on really well with Frieda", Margaret said. "She was vibrant, in a quiet way. She was lovely to chat to, and again was clever. She could quote Shakespeare, she loved the outdoors, and loved nature.

"She was beautiful and I loved her. She made Joe happy. He was more settled than with Frieda and in a better place in his head.”

(Image: manchester Evening News)

In the third week of February, when Joe visits his mother, Eileen, at her home in Wythenshawe, it seems as if something is troubling him, however.

“I got home from school and (mother) was very quiet", Margaret recalls.

"I remember her saying ‘Joe’s been. I think there’s something wrong....She was convinced he wanted to tell her something but couldn’t."

Then, on February 28, Frieda, 20, and Joe 30, are found entwined in each other’s arms in their bed at home at Hallbottom Street.

(Image: manchester Evening News)

They have each been hit at least 14 times with a large heavy hammer. Joe is laid across Frieda as if has tried to protect her.

A friend who breaks into their house, after calling twice before and getting no reply, is confronted with the horrific scene.

The couple were last seen alive at around midnight on the previous Saturday when taxi driver Joe had called to collect Frieda from the Queens Hotel.

The couple’s lifestyle, rooted in rock music, and the biker community, with friends scattered all over the country, influences the police investigation.

Officers make inquiries in London, Hampshire, Dorset, Birmingham, and Edinburgh.

Several suspects are interviewed and eliminated from inquires.

And, as with Minnie Stott's case nearly forty years earlier, it's possible stigma - and people's desire not to criminalise themselves, shaped people's attitudes about coming forward.

In Joe's case the stigma is around cannabis, which he used for pain relief, following a series of surgeries for a facial disfigurement.

“While (cannabis) was widely used among Joe’s and Frieda's circle, the impression from members of the public generally, then, was that it was frowned upon, and a lot of stigma attached to it, whereas in this day and age people may talk more openly about it, and be a lot more open minded", Det Sgt Julie Adams of GMP’s Cold Case Unit, told the M.E.N. in 2016.

“People might now air stuff that they wouldn’t at the time because it reflected badly on them.”

Certainly, Joe's family found themselves judged once the cannabis use was reported in the press.

“People my mother had known for years ignored her in the street, and parents at my school demanded that I was expelled because they reckoned my brother was a drug addict. It got really nasty", his sister Margaret said.

In 2016, police told the M.E.N that the ferocity of the attack, concentrated on the victims' head and face, suggested it was 'personal'. But the motive still isn't known.

“There were no clear arguments, or clear disagreements with people", Det Sgt Adams said. "But someone will know why it happened, and will have that key.

“The amount of blood that the person responsible would have been covered in was enormous. Someone must have seen them stained afterwards.”

Debbie's final phone call

Alicia Remorozo, a teacher in The Phillipines, and her husband Dionisio, a rice farmer, believed their daughter Debbie would be safe in England.

Her life was conservative and simple. A round of working, eating, sleeping and prayer.

By 2002 she has been working as a coronary care nurse at the Royal Oldham Hospital, for two years, one of thirty Filipinos helping ease staff shortages.

The job allows her to send money back home. And she is dedicated to it, working days of up to 14 hours, loved by other nurses as a gentle, humble soul.

But, on the morning of December 8, she fails to show up for work on ward C2. And when staff ring her flat they get no answer.

The previous day she had left work, in her uniform, wearing an orange bobble hat against the weather, just before 3.30pm.

She had started the day at 7am, and had been due to finish at 3. She stays longer - as usual - to finish up her notes. But, just before leaving work, she takes a call which, colleagues notice, seems to have left her ‘distressed’.

The next day, friends go around to her flat to find her. Using a spare key they go inside - and are met with an horrific sight.

Debbie, a devout Catholic, is lying on the floor in a crucifix position, her face covered by a tablecloth. She has been stabbed repeatedly in the neck and chest with two knives from her own kitchen.

But why?

Her flat hasn't been broken into - it seems she knew her killer and had been happy to let them in in the early evening.

There is no evidence of robbery, or a sexual motivation. But there is evidence of frenzied emotion. Anger, jealousy or hate?

Debbie was pretty and had her suitors but wasn’t so interested in boyfriends. She tended to keep them at arm’s length, although she was said to have had a relationship with a Filipino man working at a hospital in Birmingham.

(Image: Manchester Evening News)

Whatever has inspired her murder, the strong suspicion among detectives was that her killer came from inside or had close knowledge of the tight-knit Filipino community.

Indeed, a year after the murder a DNA profile officers was recovered from the seventh floor flat at Summervale House on Vale Drive, Werneth where Debbie lived and died.

However, the Crown Prosecution Service did not believe that this was enough evidence to charge the female suspect.

“I’m 100 per cent sure I know who’s done it. And people out there will know who’s done it.” said one former detective who worked on the case.

A £50,000 reward for information leading the killer is unclaimed.

Who was the man seen running from the park?

Five children depended on Elsa Hannaway, 37. And a three-year-old grandson, who called her 'mummy' too. But in the nightlife of 1980s Moss Side, Elsa could let down her hair.

On a night late in October 1987, she went out dancing and never returned home.

The next time her grandson sees her is on the news. 'There's mummy', he says, pointing at the Granada broadcast. "

That broke everyone's heart", Elsa's eldest daughter Jo-Ann, the child's mother, said of his words, in a 2016 interview with the Manchester Evening News.

Elsa was found in Whitworth Park by a jogger. A vicious sex attacker, who has never been found, had subjected her to an assault of fatal brutality.

Police try to re-trace Elsa’s every step that night. She had been out drinking at the West Indian Sports and Social Club – where she was seen dancing on her own – before she went on to the Big Western pub.

Having left with a man, who told her inquest he thought she was worse for wear, she was then seen on Quinney Crescent, where witnesses said she was knocking on doors in the hope of getting into a party.

She went back to the Sports and Social, and left at 1.15am, having been refused a lift by a man who said he wasn't going her way.

She is spotted again at 2.15am, walking home along Moss Lane East close to Whitworth Park and beside a parade of shops known as ‘The Front’.

At 3.10am, a man with dreadlocks is seen running from the park.

Eye-witness Patricia O’Loughlin is stepping out of a taxi when she sees a row between black woman and a black man on a footpath in the park.

“He grabbed her from behind and put his arms round her and pinned her arms to her side,” the witness would later tell the inquest.

She described moving away and looking back to see the woman on her hands and knees saying ‘oh my God’ with the man standing over her.

Police are sure the woman was Elsa and the man her killer. And a key piece of evidence was left behind at the scene. A Sekonda watch was found beside Elsa's body, along with her clothes. A plausible explanation is that it belonged to the killer, and came loose as Elsa struggled for her life.

This was a time when police relied more on door-to-door enquiries and tip-offs from members of the public than forensic science though. And the response from the public was poor.

Elsa's death was one of a trio of murders to occur in south Manchester within a three month period.

The two others were Geoffrey Gilbert, 43, stabbed to death in his Gorton flat, and Tony Gardner, 26, who was shot dead in Moss Side.

A year after Elsa died, Detective Chief Superintendent Grange Catlow took charge of all three. He was brutally honest.

“In the 11 years I have been charge of murder inquiries, this is the worst response we have had from the public.

"Just three telephone calls could solve these cases, but there is a general lack of interest."

The other side of the coin - that the investigation was hampered by racist policing, was alleged in a council meeting which saw investigating officers accused of 'harassment, abuse and brutality' of families in Hulme and Moss Side.

Over thirty years on from the fraught relations of the era, and Elsa's killer has still not been found.

Mother-of-three Joann told the M.E.N.: “Obviously there is someone out there who would know who’s done it or who knows something. I think it’s really sad after so many years that it’s just been left.

"She’s been forgotten. I don’t think she should be forgotten. I don’t think anybody should die on their own like that. To me it was a pointless waste of a life.

"She was 37. She was still young and able-bodied. She missed out on numerous grandchildren. It’s sad. It would be nice if somebody turned around and said ‘I remember and I need to say something’. Then she can be rested.

“There’s no way no-one knows nothing. It’s impossible. But some communities stick together and don’t want to say anything.

“It would be a big weight off my shoulders and my brothers if something came out of this. It’s been nearly 30 years. The person who did this needs to come forward and give the family some closure. It’s been a long time.”

If not the Beast of Manchester then who?

When Jimmy Ruffin played at Wythenshawe's Golden Garter on April 25, 1971, Dorothy Leyden sat in the front row. The 17-year-old was close enough to the Motown star that when he wiped his brow with a towel and chucked it into the crowd, she caught it.

The towel is still in her bag when her body is found on wasteland, behind the Spread Eagle pub on Rochdale Road, Collyhurst.

She had been walking home, having got out of a cab she was sharing with friends, at Piccadilly Gardens at 2.30am, to save a bit of money.

Recalling the incident, her sister, Pat Atkinson, said: “I remember the police coming out of the front door.

"I just went out playing and when I came in my mam called me into the living room and I think told us one at a time that Dorothy had been beaten and she had died.”

Dorothy had been sexually assaulted and attacked with a brick. Nearly fifty years on, the case remains unsolved.

In the years since, a retired detective, Ian Kirkpatrick, has suggested that Trevor Hardy, the serial killer who murdered three teenagers in districts north east of Manchester in the mid-seventies, was responsible.

Why?

Timing, geography, and the behaviour of Hardy himself.

(Image: Daily Mirror)

Firstly, in 1971 there was a spate of attacks on women in the Newton Heath area in which the victims suffered head injuries. They weren't solved, but they stopped around the time Hardy was jailed for attacking a man with a pickaxe.

Four days after Hardy was released, Dorothy was killed. Indeed, police at the time questioned him about the murder after an anonymous tipster said he had suspicious scratches on his face, but his mother gave him an alibi.

Weeks later, on New Year's Eve, Hardy murdered a 15-year-old girl.

Hardy was finally cornered in April 1976, after trying to strangle a woman in Hollinwood. He went on to confess to killing three teenagers, but not Dorothy. But, during his 40 years behind bars he suggested, entirely falsely and maliciously, that his brother Colin had done it.

Nonetheless, DNA from the scene does not match Hardy.

In 2008, Martin Bottomley, head of the force’s Cold Case Review Team, carried out a search of archives in the basement of the force's old Chester House HQ, and found swabs taken from the scene.

He then interviewed Hardy in jail, who again denied any involvement, and took a DNA swab from him.

It didn't match. Greater Manchester Police are adamant that Hardy is not the man they want, which means Dorothy's killer could still be out there.

"We do not believe it is in the interests of justice, and indeed it hampers the investigative process, to suggest Hardy murdered Dorothy", GMP said in a statement last year.

"Recollections of what was said, or not said, what happened, or did not happen, can be unreliable and certainly fade over time. The DNA evidence in this case, in the opinion of both Greater Manchester Police and the Crown Prosecution Service is incontrovertible."

Martin Bottomley, Head of GMP's Cold Case Review Unit, said about all the cases above: “GMP never closes any unsolved murder investigation and all cases are regularly reviewed by officers in the Cold Case Review Unit.

"We will follow up any and all viable lines of enquiry, whether they relate to new witness evidence or advances in forensic science.

“I would urge anyone who has any information which may assist us in bringing these offenders to justice and giving grieving family members the answers they deserve, to contact us.

“Please help us to prevent further suffering and distress.

“Information can be passed directly to officers on 0161 856 5978 or via Crimestoppers on 0800 555 111.”