On December 21, 1988, a Pan Am plane mysteriously exploded over Scotland causing the death of 270 people from 21 countries. The tragedy provoked global outrage. In 1991, two Libyans were charged with the bombing.

In the event, only Abdulbaset Ali Mohammad Al Megrahi, a Libyan agent, was pronounced guilty by a panel of three judges, who based their decision on largely circumstantial evidence. Al Megrahi and the Libyan government have protested their innocence all along.

Nevertheless, after suffering punitive UN sanctions which froze overseas Libyan bank accounts and prevented the import of spare parts needed for the country's oil industry, Tripoli reluctantly agreed to pay $2.7 billion to victims' families ($10 million per family), on condition the pay-out would not be deemed an admission of guilt.

In February 2004, the Libyan prime minister told the BBC that his country was innocent but was forced to pay-up as a "price for peace."

Al Megrahi is currently serving a life sentence, but earlier this year the Scottish Criminal Cases Review Commission ruled there may have been a miscarriage of justice on the basis of lost or destroyed evidence.

Later this month, a Scottish appeals court is due to revisit the case and is expected to overturn Al Megrahi's conviction as unsafe.

The Libyan leader's son Saif Al Islam recently said he is confident Al Megrahi will soon be found innocent and will be allowed to return home.

On Sunday, an Observer expose written by Alex Duval Smith reported "a key piece of material evidence used by prosecutors to implicate Libya in the Lockerbie bombing has emerged as a probable fake" with allegations of "international political intrigue and shoddy investigative work" levelled at "the British government, the FBI and the Scottish police."

The Observer story maintains Ulrich Lumpert, a Swiss engineer who was "a crucial witness," has now confessed that he lied about the origins of a timer switch.

Recently, Lumpert gave a sworn declaration to a Swiss court, which read "I stole a prototype MST-13 timing device" and "gave it without permission on June 22, 1989, to a person who was officially investigating the Lockerbie affair."

The owner of the company that manufactured the switch -- forced into bankruptcy after being sued by Pan Am --- says he told police early in the enquiry that the timer switch was not one his company had ever sold to Libya.

Moreover, he insists the timer switch shown to the court had been tampered with since he initially viewed it in Scotland, saying the pieces appeared to have been "carbonised" in the interim. He also says the court was so determined to prove Libya's guilt it brushed aside his evidence.

In 2005, a former Scottish police chief signed a statement alleging the CIA had planted fragments of a timer circuit board produced at trial, evidence supporting earlier claims by a former CIA agent to the effect his agency "wrote the script" to ensure Libya was incriminated.

There are also allegations that clothing allegedly purchased by the bomber in Malta before it was wrapped around the bomb, was intact when discovered but by the time it reached the court it was in shreds.

Life sentence

The shopkeeper who sold the item made a statement to the effect Al Megrahi had never been a customer. Instead, he identified an Egyptian-born Palestinian, Mohammad Abu Talb, now serving a life sentence in Sweden for a synagogue bombing.

Professor Hans Koechler, appointed by the UN to be an observer at the trial, has termed its outcome "a spectacular miscarriage of justice." Koechler has repeatedly called for an independent enquiry, which, to date, the British government has refused to allow.

Oliver Miles, a former British ambassador to Libya, insists "no court is likely to get to the truth, now that various intelligence agencies have had the opportunity to corrupt the evidence."

Jim Swire, the father of one of the Lockerbie victims, said, "Scottish justice obviously played a leading part in one of the most disgraceful miscarriages of justice in history."

Craig Murray, a former British ambassador, who was earlier second-in-command of Britain's Aviation and Maritime Department from 1989 to 1992, writes about a strange incident on his website.

Murray says a colleague told him "in a deeply worried way" about an intelligence report indicating Libya was not involved in the Pan Am bombing. When he asked to see it, his colleague said it was marked for named eyes only, which Murray describes as "extremely unusual." Earlier, a CIA report that had reached a similar conclusion had been conveniently buried.

If Al Megrahi walks, as is likely, Libya will be vindicated and would presumably be able to reclaim monies paid in compensation along with its reputation.

This would also be a highly embarrassing turn of events for Britain and the US, not to mention their respective intelligence agencies, and would leave the question of who bombed Pan Am Flight 103 unanswered.

In a perfect world, Libya should also receive an apology from its accusers and should be allowed to sue for damages for all that it lost as a result of UN sanctions.

But in a world where political expediency often triumphs, the appeal has no foregone conclusion despite the exposure of dubious "evidence" and suspect "witnesses."