IT IS one of the longest-running unsolved disappearances in Scotland, dating back to 1967, when a young Dumfries woman who had been on a trip with a friend to Glasgow failed to come home.

Fifty years on, police sources are still convinced 17-year-old Patricia McAdam was killed by Thomas Ross Young, but there was never enough evidence to convict him.

The man believed to have killed the teenager was already serving a life sentence for the murder of bakery worker Frances Barker, 39, who was abducted near her home in Maryhill in Glasgow in June 1977, and whose strangled body was found in woods in Glenboig, North Lanarkshire, when he was laterally charged with killing Miss McAdam.

By then he had been found guilty of a host of criminal acts including two attempted murders, two rapes and other offences.

However, no body was found in the search for Miss McAdam.

Miss McAdam went missing after hitching a lift in a lorry driven by Young following the trip to Glasgow.

The case led to a massive police search but it was not until years later that any breakthrough came

Young, who was alleged to have murdered her on a road near Dumfries, was fully committed and remanded in custody.

Young was charged after a cold case review in 2007 but the case never came to trial.

Miss McAdam had been due to return to her home at Lochside Road in Dumfries following a shopping and dancing trip to Glasgow, and along with a friend had hitched a lift on the A74 road from a lorry which dropped off her friend in Annan and was last seen heading for Dumfries.

Throughout the weeks, months, and years following, intensive searches were carried out by police and volunteers along roadsides, woods, and riverbanks.

Her late parents Matthew and Mary McAdam put in their own efforts travelling hundreds of miles following up reports of sightings, asking questions and living in hope but no trace was found.

Young, the lorry driver who had given Miss McAdam a lift, appeared via a video link from Peterhead Prison to Dumfries Sheriff Court and was charged her murde on the B7020 Lochmaben to Annan road near Charlesfield Farm on February 19, 1967, by means unknown.

The case, however, never came to trial with the Crown Office later stating that there should be no proceedings “against this individual meantime.”

Believed to be an associate of World's End killer Angus Simpson, Young spent 37 years behind bars for the abduction and murder of Frances Barker.

Young, who was serving life sentences for murder, attempted murder and rape and who suffered from a heart condition, died in 2014, at the age of 79.

A legal source said that at the point of Young's death "the report was still under review and would have considered further evidence that came to light however, detailed enquiries which followed his initial appearance established that there was insufficient evidence to prosecute him".

A Crown Office spokesman said: "The Crown conducted extensive inquiries into these allegations, and established that there was insufficient evidence to prosecute Thomas Ross Young for the murder of Patricia McAdam.

“This decision was based solely on the evidence in this case, and like any unresolved homicide the case remained under review, however no further evidence emerged prior to the death of Thomas Ross Young in 2014.”