Former Lord Advocate Colin Boyd, now a consultant at Dundas and Wilson, has publicly defended the “robust” conviction of Abdelbaset Ali Mohmed Al Megrahi and claimed that he, his predecessors and successors in office were all “satisfied that there was either sufficient credible evidence to prosecute or, in my case, and Elish’s, that the conviction on that evidence was sound.”

Boyd also rejected a suggestion published yesterday in The Times from Professor Robert Black QC that the three Camp Zeist trial judges may have “subconsciously” been unwilling to undermine the Lord Advocate’s judgement in bringing the Pan Am 103 case to trial, by returning not guilty or not proven verdicts.

“It’s a frankly pretty ludicrous allegation - a slur on the reputation of judges who are all very senior and experienced,” Boyd said.

“I had been in office for all of three months when the trial took place, so I could not possibly have been responsible for their appointment. Had I been, there is no question of my having a hand in influencing them. This is not the culture of the Scottish judiciary. I utterly reject the suggestion.”

“Every Lord Advocate from Peter Fraser to Elish Angiolini has examined the evidence at one time or another - six in total.

“All were satisfied that there was either sufficient credible evidence to prosecute or, in my case, and Elish’s, that the conviction on that evidence was sound. Not one of us would have prosecuted or defended the conviction if we considered that there was any doubt. The process was robust and the conviction sound.”

Professor Black’s suggestion was originally published some four years ago, and reiterated at a Q&A session following a public performance of David Benson’s one-man stage show ’Lockerbie: Unfinished Business’ at the Edinburgh Fringe on Monday afternoon. In 2007, Black said:

“It has been suggested to me, very often by Libyans, that political pressure was placed upon the judges. I don’t think for a minute that political pressure of that nature was placed on the judges.

“What happened, I think, was that it was internal politics in Scotland. Prosecutions in Scotland are brought by the Lord Advocate. Until just a few years ago, one of the other functions of the Lord Advocate in Scotland was that he appointed all Scottish judges.

“I think what influenced these judges was that they thought that if both of the Libyans accused are found not guilty, this will be the most fiendish embarrassment to the Lord Advocate."

In response to Boyd’s comments, Black said this morning that Boyd has overlooked that: “one of the six grounds upon which, after a three-year investigation, the Scottish Criminal Cases Review Commission found that Megrahi's conviction might have amounted to a miscarriage of justice, was that, on the evidence led at Camp Zeist, no reasonable court could have reached the conclusion that Megrahi was the purchaser on Malta of the clothes that surrounded the bomb.

“Without that finding in fact, Megrahi could not have been convicted,” he added.

Lord Maclean, one of the three trial judges who acted uniquely as jurors in this case for the first time in their careers, in his only interview on the subject given to The Firm’s Editor Steven Raeburn in 2005, gave a carefully qualified and hedged defence of the unanimous split verdicts in the case.

“I have no doubt, on the evidence we heard, that the judgments we made and the verdicts we reached were correct," he said.

In February this year the Scottish Parliament was urged to undertake an investigation into the legal advice provided by the former Lord Advocate, Elish Angiolini, in her role as legal adviser to the Scottish Government over the Pan Am 103 debacle.

The committee highlighted errors in her legal assessment of the Megrahi case, and challenged “the quality and accuracy of the advice and information being given to the Scottish Government by Scotland’s senior Law Officer.”

In June this year Lord [Peter] Fraser was challenged by Dr Jim Swire to explain his position after he told an Al Jazeera documentary film crew that he accepted a key witness in the Pan Am 103 trial had been bribed by Scottish Police.

The Scottish Parliament’s Justice Committee will consider whether an inquiry into the affair is to be constituted in the new Parliamentary session.