A convicted paedophile who was questioned over the disappearance of a Bonhill teen - who vanished more than four decades ago - has died.
Norman Duncan, 75, was found dead at his home in Ladyton last week.
Police Scotland confirmed officers had been called to an address in the Bonhill neighbourhood following a sudden death and confirmed there were no suspicious circumstances.
A spokesperson said: “Around 8.35pm on Wednesday, May 25, police were called to a property in Ladyton, Bonhill, following the sudden death of a 75-year-old man.
“There are no suspicious circumstances surrounding the death and a report will be sent to the Procurator Fiscal.”
The pensioner was investigated by police over the disappearance of his stepdaughter Mary Duncan, who was last seen in 1976, aged 17.
Despite extensive searches for Mary, including at Norman Duncan’s home, the Vale of Leven Hospital and in Helensburgh, her case remains unsolved.
Officers swooped on Duncan’s house in 2019 in the hope of clues after launching a fresh missing persons probe.
Police would not confirm the search was linked to the missing girl, but her sister Mandy Duncan said at the time: “We are praying that there is something in that house which will lead us to Mary and bring us closure.
"All we can do now is wait — we just want it to be over.”
A forensic team combed through the terraced house during a seven-day search, while Duncan was behind bars for twisted crimes.
In 2016, he was convicted of impregnating a 15-year-old girl and sexually abusing three children nearly half a century earlier.
He was found guilty of six charges involving four girls aged between eight and 15, all committed between the 1960s and 1970s, and received a five-year prison sentence.
After completing his jail time, he returned back to his home in Ladyton.
Searches also took place at the Vale of Leven Hospital in 2020, where Mary frequented, and land in a residential area of Helensburgh was also searched later that year.
Heartbroken sisters Debbie Renwick, Mandy Duncan and Marion McFarlane made an emotional plea for information after a new probe was opened in 2018, describing her as a “devoted mother” and “quiet, happy girl”.
She vanished without a trace after leaving her home in Third Avenue, Bonhill, on March 19, 1976 to visit a friend in Tullichewan.
The teenager left behind a daughter Laura, who she adored, born on February 17, 1975. Baby Laura tragically died of natural causes the following year.
Mary was wearing a navy skirt, black platforms, a green hoodie and a black and white dogtooth coat when she was last seen.
Detectives have told how they believe vital clues about what happened to Mary, who worked as a machinist in Rosshead, lay within the community of West Dunbartonshire.
While stressing it is a missing persons probe, officers said they could not rule out the possibility that Mary has come to harm.
Speaking at a press conference during the re-appeal for information, Detective Superintendent Calum Young said: “Mary’s family were left devastated by her disappearance, a pain which lives with them to this day and it is vital that we get to the bottom of what happened to their sister and provide them with some closure.”
He admitted it was a “challenging” investigation given the passing of time and said any new technologies would be utilised to their full effect, adding: “Every resource is at our disposal.”
A Police Scotland spokeswoman confirmed enquiries into Mary’s disappearance remain ongoing.
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