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But one of Scotland’s universities is now hoping to solve some of these cases with the creation of a new cold case unit.
Criminology students at Glasgow Caledonian University will review case files and search for new evidence, working alongside the families of missing loved ones and specialists in investigation, forensic science and intelligence analysis.
The university will develop the cold case unit in partnership with Locate International, a community interest company that works with higher education institutions to help progress historical cases. There will be 14 students involved initially and the cases, although yet to be assigned, will be Scottish based.
Dr Maureen Taylor, criminology lecturer and director of the cold case unit and former forensic investigator and criminal intelligence analyst, said: "Some of these cases are decades old and have caused families a huge amount of distress.
“Working with Locate International and developing the cold case unit is a unique collaboration that offers the opportunity to not only give hope to the families of missing loved ones but to develop novel solutions to cold case investigations and analytical capabilities.
"The cold case unit will provide students with the opportunity to receive fantastic training in investigation, intelligence and analysis.
"It is a very exciting project that will help to not only develop future investigators but also bring answers to families of the missing."
It is hoped the students will begin training in the summer and that work on the first case will start in September.
Figures show there are more than 4,000 people in the UK who have been missing for more than a year and there are around 1,000 unsolved cases involving unidentified human remains.
Here are some of the unsolved missing persons cases in Edinburgh, the Lothians and Fife.
Thomas Saunders was last seen at the Premier Inn, Leith, on December 16 in 2018. His blue Volkswagen Golf GTI - registration number S274 OGB - was later discovered, apparently abandoned, near to a forestry track in Ardgartan in Argyll. His route there is unknown but the car is thought to have been at the location it was found since December 18 or 19, 2018.
Mr Saunders, from Muirhouse, is described as white, of medium build, with green eyes and short white or greying hair. He was 58 at the time he disappeared. Police have regularly appealed for anyone who may remember seeing his car being driven in the Arrochar or wider Argyll area, or any walkers or cyclists who may recall seeing him, to get in touch.
John Coleman was 51 when last seen at the Access Point in Leith Street on May 1, 2009. He is known to live rough and travel extensively throughout the UK and Ireland. He also goes by the names Daniel and Sean O’Connell.
Mr Coleman has two distinctive tattoos on his left arm. He has ‘John’ tattooed on his forearm and another with a rose, dagger and Irish harp. He is described as being white, around 5ft 9ins tall, of medium build with brown eyes. He has medium-length brown hair and is unshaven and speaks with a Glasgow accent.
Iain McLean was 24 when he left his family’s Edinburgh home - one of the colony houses in Ashley Terrace, Shandon - without his glasses, passport or any money on Friday, December 8 in 1995. He was last seen by his mother at around 6pm that evening before she went out for a meal - but when she returned he had gone.
In December his sister, Shona Mathers, told the Edinburgh Evening News her sibling had been struggling with deteriorating mental health at the time he disappeared following a relationship break-up in Italy, where he had been teaching English. He had also been diagnosed with depression and struggled with work and sleep.
Mr McLean is described as 6ft tall, of slim build with curly, black shoulder length hair at the time he went missing. He also has a noticeable scar on the side of his left eye. He would now be 49 years old.
Allan Bryant was 23 when he was last pictured on CCTV outside a nightclub in Caskieberran Road in Glenrothes, shortly after 2am on Sunday, November 3, 2013. The previous night, he walked with friends to an engagement party at Leslie Golf Club from his Ednam Drive home.
He arrived at the golf club at 9pm and left around midnight when he travelled by minibus to Styx nightclub. Mr Bryant and the group arrived at Styx shortly after and left the club, which is about one mile walk away from his home, at 2.02am. Despite extensive searches and public appeals from his family, he has not been heard or seen since.
Mr Bryant is described as white, 5ft 6ins tall, of medium build with short brown hair, blue eyes and tattoos on both arms.
Peter McGuire went missing from the village of High Valleyfield in Fife on Wednesday, January 27, 1993, at the age of 21. He was seen later that day leaving Carnegie swimming pool in Dunfermline. An investigation was launched which resulted in his car being recovered near to the Forth Road Bridge - but there were no further sightings.
However in November 2016, information was received that a man using Mr McGuire’s name and date of birth had been living rough in the Hastings area of England and this information was progressed by police. It was established he had quickly moved on, possibly to the West London area. Police are continuing to try and identify this man.
Mary Ferns was 88 when she left her home in the Howden area of Livingston around 9.30am on June 17, 2008, telling her husband she was heading to the Almondvale shopping centre to buy tights. She had a floral-patterned walking stick with her at the time.
But it is believed she got on a bus as family members identified her through CCTV images on Edinburgh’s Princes Street. This was the last known sighting of the pensioner.
Human remains were found at the edge of the River Almond in 2010 which were thought could have been Mrs Ferns - but they turned out to be those of another man, James Adams, who had disappeared 15 years earlier.
Alexander ‘Sandy’ Joseph Clarke
Alexander ‘Sandy’ Joseph Clarke went missing from Kirkcaldy on Tuesday, May 4 in 2013. Then aged 37, he was last seen around 2am that morning leaving the town’s Victoria Hospital and walking east along Hayfield Road. He was carrying two Sports Direct bags containing clothes.
He is described as 5ft 10ins tall, of slim or average build with short, slightly receding brown hair and brown and green eyes. He has tattoos on both arms and a tattoo on his neck of a woman’s name.
Kenneth George Jones
Kenneth George Jones was last seen at 7am on Tuesday, November 3 in 1998 when he left his home in Ancrum Court, Glenrothes. He was 18 years old at the time.
He is described as white, 6ft 2ins tall, with short dark brown hair. He was last seen wearing a black blouson style leather jacket with zipped front, black jeans, yellow and green trainers and carrying a small black and blue rucksack. He has a small scar under his right eye.
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