A BBC Newsnight investigation has cast fresh doubts on a key piece of evidence in the Lockerbie trial which linked the bomb which downed the Pan Am jet to Malta.
270 people died in the 1988 attack on Pan Am flight 103.
The BBC said tests aimed at reproducing the blast appeared to undermine the case's central forensic link, based on a tiny fragment identified as part of a bomb timer. The tests suggested that the fragment, which linked the attack to Malta and to Abdelbaset Ali al-Megrahi, would not have survived the mid-air explosion.
Two hundred and seventy people died in the 1988 attack on Pan Am flight 103.
"I do find it quite it extraordinary and I think highly improbable and most unlikely that you would find a fragment like that - it is unbelievable UN European consultant on explosives, John Wyatt, said.
The fragment was found three weeks after the attack. For months it remained unnoticed and unremarked, but eventually it was to shape the entire investigation. The fragment was embedded in a charred piece of clothing, which was marked with a label saying it was made in Malta.
So the focus turned to Malta and the question of who had bought the clothes.
A Maltese shopkeeper identified al-Megrahi, but this came only years later after he saw him pictured in a magazine as a Lockerbie suspect. Al-Megrahi was subsequently convicted and jailed but was released on humanitarian grounds after being found to suffer from advanced cancer late last year.
BBC Newsnight said it had discovered that the fragment - crucial to the conviction - was never subjected to chemical analysis or swabbing to establish whether it had in fact been involved in any explosion.
Consultant John Wyatt said he had recreated the suitcase bomb which destroyed Pan Am 103, using the type of radio in which the explosive and the timer circuit board were supposedly placed, and the same kind of clothes on which the fragment was found.
In each test the timer and its circuit board were obliterated, prompting Mr Wyatt to question whether such a fragment could have survived the mid-air explosion.
"We carried out 20 tests, we didn't carry out 100 or 1,000, but in those 20 tests we found absolutely nothing at all - so I found it highly improbable that you would find anything like that, particularly at 10,000 feet when bits are dropping into long wet grass over hundreds of miles," Mr Wyatt said.
http://news.bbc.co.uk/2/hi/uk_news/8441796.stm