During its four-year investigation, as well as finding six grounds why Megrahi may have suffered a miscarriage of justice, the Scottish Criminal Cases Review Commission (SCCRC) examined numerous other issues which, according to his lawyers, affected the safety of his conviction.

Prime suspect No.2

The most unusual Crown witness at Megrahi's trial was convicted terrorist Mohamed Abu Talb, who was serving a life sentence in Sweden for fatal bombings in Northern Europe in the mid-1980s. Previously a prime suspect in the Lockerbie bombing, he had visited Malta two months before Lockerbie, returning with clothes. Some of his associates had visited the German flat in which Marwan Khreesat, of the Popular Front for the Liberation of Palestine-General Command (PFLP-GC), made barometric bombs. When Megrahi became a suspect the trail to Abu Talb went cold and by calling him as a witness the Crown attempted to demonstrate that he could not have been responsible for Lockerbie.

The SCCRC uncovered no significant new evidence about Abu Talb, but was unable to properly investigate an airline ticket, which suggested that he possibly made a second trip to Malta at around the time that Tony Gauci said he sold the bomb suitcase clothing.

The commission requested that Dumfries and Galloway Police ask the officers involved in inquiries relative to Abu Talb whether they had established the position in respect of the return portion of the ticket.

The force confirmed in a letter dated April 19, 2006, that none of the officers could recall making inquiries in this connection. In the commission's view, although regrettable that the matter was not checked with Scandinavian Airlines at the time of the police investigation, there was no failure by the Crown to disclose material evidence about the return portion of Abu Talb's flight ticket.

There is no smoking gun to implicate Abu Talb, but his trip to Malta and his PFLP-GC connections continue to fuel suspicions of his involvement in Lockerbie.

'The Golfer'

The Golfer was the cover name of a police officer who told Megrahi's then legal team that key items of evidence had been manipulated to fit the prosecution case. Subsequent submissions to the SCCRC by former lawyers for Megrahi MacKechnie & Associates highlighted anomalies in police documentation, which appeared to support these claims. The commission investigated the allegations, and interviewed the Golfer three times, but found nothing to substantiate the allegations.

It said: "While some of the allegations made in the submissions were based upon information said to have been provided by the Golfer, others were based purely on perceived irregularities in the recorded chain of evidence.

"The commission's approach to the latter was that in any police inquiry, let alone one as large scale and complex as the present one, human error is inevitable.

"Although apparent omissions, inconsistencies or mistakes in productions records may, after a long period of time, appear difficult to explain, or even suspicious, in the commission's view they do not support allegations of impropriety against those involved in the investigation."

The police will be relieved by the report's conclusions. That relief won't be shared by the Crown Office, which the SCCRC has left with some important questions to answer.

The defence lawyers

Megrahi's application to the SCCRC argued that the approach of his original defence team had contributed to his wrongful conviction. In interviews with the commission, Megrahi's former solicitor Alastair Duff, leading counsel Bill Taylor, QC, and junior counsel John Beckett all robustly defended their handling of the case.

The report concludes: "In the commission's view there is nothing in the submissions under this heading, or in the accounts given by the former representatives at interview, which supports the submission that the conduct of the defence was such as to deny the applicant a fair trial. Accordingly the commission does not consider that a miscarriage of justice may have occurred in this connection."

Overturning Megrahi's conviction on the grounds of defective representation was always going to be difficult. It remains to be seen whether this will be a ground of appeal if the conviction is ever referred back to the high court.

Megrahi himself

Before referring Megrahi's conviction to the appeal court, the SCCRC had to be satisfied that, regardless of the weaknesses in the Crown case, there was not overwhelming evidence of his guilt. In practice this meant exploring the issues that would have been raised during cross-examination, if he had opted to give evidence. These included his relationship with the Libyan Intelligence Services (JSO), his use of a false passport, and lies he had told in a US television interview.

The report says: "While at no time did the applicant admit that he was a "member" of [the JSO], in the commission's view he was so closely associated with it as to amount to the same thing - it is important to bear in mind in any assessment of the applicant's accounts that each of them was given in English rather than in his native tongue.

"It is obvious - that on occasions the applicant had difficulty expressing himself clearly. Caution is therefore required in analysing his accounts - on the other hand, the applicant speaks English relatively well, having previously studied the subject in Cardiff, and he did not request the assistance of an interpreter at any stage in his interview with the commission.

"In these circumstances the commission does not consider the inconsistencies in his accounts are merely the result of communication difficulties - in particular, the commission believes there was a real risk the trial court would have viewed his explanations for his movements on 20 and 21 December 1988, and his use of the [false] Abdusamad passport on that occasion, as weak or unconvincing.

It concluded: "The commission has also considered whether, notwithstanding its conclusion that a miscarriage of justice may have occurred, the entirety of the evidence considered by it points irrefutably to the applicant's guilt. The commission's conclusion is that it does not."

Megrahi insists he had nothing to hide from the SCCRC and the inconsistencies in his accounts are innocent. While he disputes some of its conclusions he has made clear he is happy for them to be made public.

l John Ashton is the author of Megrahi: You Are My Jury. He will be speaking at Aye Write tonight. See www.ayewrite.com