Two carers who murdered a vulnerable teenager whose body has never been found have each been ordered to spend a minimum of 14 years in prison.
Edward Cairney, 77, and Avril Jones, 59, killed Margaret Fleming, 19, between December 1999 and January 2000.
Jones then continued to claim £182,000 in benefits until it finally emerged Margaret was missing in October 2016.
At the High Court in Glasgow Lord Matthews told Cairney he must serve at least 14 years.
Jones’ minimum life tariff was also set at 14 years.
She was also found guilty of benefit fraud as Margaret’s money was paid directly into her account.
Lord Matthews told them: “Only you two know the truth. Only you know where her remains are.”
Thomas Ross QC, for Cairney, said his wheelchair bound client had his colon removed a few years ago after he contracted an infection.
He also suffers from hip damage and the after effects of breaking three vertebrate.
Mr Ross said: “Mr Cairney continues to deny any involvement in the crime and, so far as he is concerned, he maintains that, to his knowledge, Margaret is still alive.”
Iain Duguid QC, for Jones, said his client was diagnosed with peripheral neuropathy, a condition which affects the nervous system, in 1994.
The court heard the case has left Jones, a former legal secretary and greenkeeper, “isolated” from her friends and family.
The QC said his client also maintains her innocence and that, as recent as their last contact in October 2017, Margaret was still alive.
Despite a painstaking search of their dilapidated property in Inverkip on the Clyde coast, and its garden, no trace of Margaret has every been found.
Testimony from Avril’s brother, Richard Jones, was used to pinpoint the last independent sighting of the teenager on 17 December, 1999.
Three weeks later, on 5 January, 2000, Avril told her mother, Florence Jones, Margaret had run off with a traveller.
The couple, who had no previous convictions, then embarked on a cover up which involved bogus letters and erasing all trace of Margaret from the cottage where she had lived for around two years.
The catalyst for the teenager moving in with the couple was the death of her father in 1995.
Cairney, who was his friend, offered to help and took advantage of Margaret’s strained relationship with her mother.
All ties between the pair were severed in November 1997 when Cairney assaulted Margaret Cruickshanks after she arrived at Seacroft to see her daughter.
Thereafter the couple took control of the teenager’s life and subjected her to what police described as a “living hell”.
Police and prosecutors narrowed the timeframe of the murder to a three-week period around the turn of the millennium.
The trial heard that a benefits investigator attempted to visit Ms Fleming in June 2012 but was told by Jones that she would not see her.
The investigator said a duty social worker should have visited the “totally chaotic” property to follow up on the young woman’s welfare, but no-one did.
When police were finally alerted four years later it was as a result of an application for Personal Independence Payments (PIP) – which had been filled out by Jones.
In it she wrote that Ms Fleming “needs constant care”, had self-harmed and was “caught eating out of a dog bowl”.
A social worker phoned Jones to offer help and was told Ms Fleming had not been to the doctor, despite picking a hole in her head.
Police Scotland subsequently launched a missing persons’ investigation in October 2016.
When justice eventually caught up with the couple a year later they maintained Margaret was still alive and often returned to visit them.
Cairney even gave evidence in his defence, during which he was warned by the judge for insulting prosecutor Iain McSporran QC.
But an exhaustive investigation failed to find any trace of the teenager and the jury took just three hours to find the pair guilty.