FRESH doubts have been raised over the conviction of the Lockerbie bomber after the reliability of a key witness was called into question.
There are concerns about the evidence of prosecution witness Alan Feraday, who testified during the trial of Abdelbaset Ali Mohmed al-Megrahi.
It has emerged that three men who the forensic scientist also gave evidence against have since had their convictions quashed.
Papers about Mr Feraday's evidence have now been sent to the Scottish Criminal Cases Review Commission, which was investigating Megrahi's conviction.
A total of 270 people died when the American passenger jet Pam Am 103 exploded over the Scottish town of Lockerbie on December 21, 1988.
In 2001, judges at a special court at Camp Zeist in Holland found Megrahi, 52, guilty of murder. His co-accused, Al Amin Khalifa Fhimah, was cleared.
An appeal made later by Megrahi was refused.
During the trial, Mr Feraday, who is now said to have retired after 42 years experience in explosives, told the judges that he was in no doubt that a circuit board fragment found after the disaster was part of the detonator. The trial judges accepted his conclusion.
However, in three separate cases, men against whom Mr Feraday gave evidence have now had their convictions overturned, the latest last month.
The commission will now consider whether the Lockerbie trial judges should have given so much weight to Mr Feraday's evidence.
Solicitor Eddie McKechnie, who represented Megrahi at the Lockerbie trial, said that it provoked "serious issues" about the conviction.
He said: "It is a factor that I take very seriously into account on behalf of Mr Megrahi.
He added: "One would have thought that when a professional and a government forensic expert is impugned in a number of cases, then serious issues arise."
Dr Jim Swire, who led the campaign for justice after losing his daughter Flora in the bombing, said the revelation "undermines one's confidence" in Megrahi's life sentence.
He said: "I'm personally not satisfied of Mr Megrahi's guilt.
"I emerged [from the trial] riddled with doubts.
"This will of course augment them."
He added: "If one finds that three cases have been overturned, it rather undermines one's confidence."
Former Libyan secret agent Megrahi is serving a 27-year sentence for the bombing.
Passing sentence, Lord Sutherland said it would have been longer but for the fact that the Libyan was in a foreign country and was held virtually in solitary confinement.
The Crown is appealing against what it believes is an "unduly lenient" prison term.
Megrahi was originally housed in a specially-built 250,000 Barlinnie suite, dubbed "Gaddafi's Caf" where he had little contact with his fellow inmates for fear of reprisals.
But earlier this year, it emerged he had been transferred to a standard cell in Greenock Prison.
Insurers for former US airline Pan Am have also gone to court in an attempt to sue Megrahi.
Pan Am lost 282 million and went out of business as a result of the atrocity. Megrahi has denied liability.