Evidence against Megrahi fell under a number of headings.
1. A member of the Libyan security services who had turned CIA informer identified him as a senior security operative.
2. Tony Gauci identified him as 'resembling' the man who bought the clothes in his shop.
3. He was shown to have been at Luqa airport at the time KM180 departed, travelling on a false passport.
4. Baggage transfer records at Frankfurt showed evidence of an item of luggage being transferred from KM180 to PA103A, even though no passenger from the Malta flight was booked on the Heathrow flight, and all the passengers collected their luggage at their destinations with nothing going astray.
5. A small piece of printed circuit board found embedded in a scrap of the Maltese clothes was identified as a part of a countdown timer made by a Swiss firm which Megrahi had had business dealings with. This timer was part of a special order of only 20 items supplied exclusively to Libya.
The difficulty with this is firstly that each of these points fails to stand up to serious scrutiny, and secondly that far more robust evidence exists for both a different modus operandi and a different set of perpetrators.
1. Membership of the Libyan security services
The CIA informant, Majid Giaka, was originally the Crown's star witness. Without his evidence, the indictments against Megrahi and his colleague Lamin Fhimah (who was acquitted) could not have been issued in the first place. However, CIA cables revealed during the trial exposed Giaka as a fantasist who was inventing 'intelligence' for favours and money from the CIA. The judges discounted all his evidence except for his statement that Megrahi was a member of the Libyan security forces. No other evidence for this was produced, and Megrahi has consistently denied the allegation. No evidence has ever emerged linking Megrahi to any other terrorist atrocities or human rights abuses of the Gaddafi regime, or to refute his claim that he was merely an airline employee who was also moonlighting as an entrepreneur businessman.
2. The identification evidence
Tony Gauci was first interviewed about the clothes sale on 1st September 1989, nine months after the event. He described the purchaser as Libyan, aged about 50, over six feet tall, heavily built and dark-skinned. Megrahi is 5 feet 8 inches tall, light-skinned, of medium build, and was 36 at the time of the purchase. A photofit and an artist’s impression produced at the time suggest the man may have been negro or mixed race. Gauci was unsure of the date, but this was narrowed down to either 23rd November or 7th December 1988 on the basis of televised football games. Gauci stated that the Christmas lights were not yet lit, and it was raining when the customer left the shop.
On 15th February 1991 (well over two years after the purchase) Gauci was shown a police photospread including a picture of Megrahi. He initially rejected all the men as being 'too young', but when urged to reconsider he chose Megrahi's picture as the one that looked most like the customer. However, all the policemen present knew which picture was the suspect's, a recognised confounder in such exercises and something now banned, and Megrahi's picture was appreciably different from the others in both size and quality. As a further confounder the passport photo reproduction used was such a poor likeness of Megrahi as to be essentially unrecognisable. It did, however, look a bit like the photofit Gauci had produced in 1989.
By the time of the live identity parade in April 1999, better likenesses identifying Megrahi as the 'Lockerbie bomber' had appeared in many publications, which Gauci is known to have seen. (So widespread had been the publicity that most people following the case could probably have picked the accused out without ever having met him.) Megrahi was by then 47, close to the age the purchaser was said to be in 1988. The 'foils' in the parade were nearly all much younger (and bore little resemblance to Megrahi), even though by Gauci's original estimate the purchaser would by then have been in his early sixties. Megrahi in the flesh looked nothing like the images Gauci had produced for the police in 1989, or the blurry passport photo he picked out in 1991. Nevertheless, Gauci once again fingered him as 'resembling' the purchaser.
The date of the purchase was important, as Megrahi was in Malta on 7th December 1988 (using his own passport), but not on 23rd November. Meteorological evidence demonstrated that there was light rain in Sliema at the relevant time on 23rd November, but not on 7th December. The Christmas lights were eventually found to have been switched on on 6th December.
In late 1998 a magazine article was published with a recognisable photograph of Megrahi, together with a list of all the discrepancies between Gauci's original description of the purchaser and date, and the case against Megrahi. Gauci had a copy which was only taken from him four days before the identity parade. When he gave evidence, he consistently back-tracked on his original statements regarding height, build, age, Christmas lights and rain, always to favour the prosecution case. Tony Gauci's brother Paul, who was later rewarded for 'maintaining the resolve of his brother', had long expressed interest in a reward for the family's input, and after Megrahi was convicted the brothers were paid an alleged $3 million by the US Department of Justice's 'Rewards for Justice' programme.
3. Presence at Luqa airport
Megrahi was at Luqa airport on the morning of the disaster, using a passport in the name of 'Abdusamad'. However, all he did was catch his flight for Tripoli, without going airside, and without checking in any hold luggage. The court accepted that he could not have got the bomb suitcase on to KM180 himself, and must have had an accomplice. That accomplice was originally said to have been Lamin Fhimah, but Fhimah could not even be shown to have been at the airport that morning. The 'false' passport was a legal one, issued to Megrahi to allow him to conceal his airline employment while negotiating business deals to circumvent the sanctions then in force against Libya, and which he occasionally used for personal travel. Although Megrahi used it for that trip, he had business meetings in Malta using his own name, and stayed at a hotel where he was well known.
Not only was no other accomplice identified, security at Luqa airport was unusually tight in 1988, and baggage records provided strong evidence that there was no unaccompanied luggage on flight KM180. Despite intensive and intrusive investigation lasting many months, no plausible mechanism whereby the bomb suitcase could have been loaded was ever identified, and no trace of the bomb was found on the island.
4. Baggage transfer at Frankfurt
The only evidence for an unaccompanied suitcase coming from Malta was a single line of code in a printout taken from the Frankfurt airport automated baggage system, which surfaced in August 1989. However, that system was far from transparent, and a number of guesses and assumptions were necessary to conclude that something might have been transferred from KM180 to PA103A. In the end, two items apparently loaded on to the Heathrow flight could not be identified, one seeming to have come from Malta and one from Warsaw. The coincidence of the Maltese clothes caused the investigators to become convinced the former item was the bomb, and this was never reconsidered despite the failure to find any way the bomb could have been put on board at Luqa. The Warsaw-origin item was never investigated.
5. The timer fragment
This is the most notorious item in the Lockerbie case. Originally the investigators believed the bomb to have been triggered by an altimeter device, operating on air pressure, and designed not to explode until the device was airborne (...) This introduced problems in respect of a Frankfurt introduction, as such a device should have exploded over France. A hypothesis was developed that the altimeter had malfunctioned on the feeder flight, only to detonate after the second take-off. When the focus of the investigation switched to Malta and a third flight, this introduced a paradox that was not addressed for over a year, until the identification of this fragment as part of a countdown timer resolved the difficulty.
The MST-13 timer was said to be one of a special run of only 20 supplied exclusively to Libya by the Swiss firm MEBO. Megrahi had business dealings with that firm, but not relating to, or at the time of, the purchase of the timers. Nevertheless this was said to be the 'golden thread' linking him to the bomb. This item had extraordinarily irregular provenance within the forensic investigation, with paperwork anomalies leading many commentators to suspect its appearance in the chain of evidence had been back-dated. In addition, the Libyan provenance was less certain than claimed, with Lockerbie occurring over two years after the timers were supplied, and examples having been found in other parts of Africa.
Irrespective of who had bombed the plane, the countdown timer introduced another paradox. Maid of the Seas exploded only 38 minutes after her wheels left the tarmac, and the plane was not late. There was a seven-hour flight ahead of her, with a thousand miles of Atlantic ocean where incriminating clothes and PCB fragments could have been buried forever. An altimeter timer would inevitably have exploded around 40 minutes into the flight, regardless of take-off time. Using a countdown timer set so early in the flight time carried a huge risk that the explosion would have occurred harmlessly on the tarmac if the plane had missed its slot at Heathrow – as could easily have happened on a stormy winter evening.
It was only in February 2012 that metallurgical evidence concealed from the original trial was revealed, which showed that the fragment could not have been one of the 20 items MEBO had supplied to Libya. This discovery calls into question whether the PCB chip was even part of a countdown timer, rather than some other electronic component using the same basic template.
[Another critique of the evidence against Megrahi can be read here.]