A statement issued by the Crown Office which attempted to undermine MSP Christine Grahame does not challenge the key claim made by Grahame that the chain of evidence in the Lockerbie case was broken.

A fragment relied upon by the Crown during the trial travelled to the US and Germany, and Grahame said Scottish police investigators did not record the fragment’s transportation across the world and in doing so broke the vital chain of evidence undermining the integrity of the fragment.

“Questions also need to be answered about the associated evidence log that was meant to accompany PT-35. It mysteriously does not record that the fragment went to the US or Germany, even though the Crown Office has confirmed in writing that it definitely went to Germany," she said.

The Crown Office quickly issued a statement accusing Ms Grahame of promulgating “misleading” information, although crucially they did not deny the truth of Grahame’s story, and offered no explanation as to why the "chain of custody" label attached to the evidence fragment appears not to record the movements out of the country.

In 2007, MEBO engineer Ulrich Lumpert submitted an affidavit stating that the circuit board fragment produced in court at Zeist was part of a non-operational demonstration circuit board that he himself had removed from the premises of MEBO and had handed over to an investigator on 22 June 1989, six months after the destruction of Pan Am 103.

“If this is true, then it totally demolishes the prosecution version of how the aircraft was destroyed, as well, of course, as demonstrating deliberate fabrication of evidence laid before the court,” Professor Robert Black said at the time.

Former Police Investigator Stuart Henderson has stated on the record that if the crucial fragment had travelled abroad without being recorded, it would be tainted evidence and considered unreliable by the court.

“We couldn’t afford to let something like that go. It has never been in their [US] control at all. It couldn’t be, because it was such an important point of evidence it wasn’t possible to release it,” he said.

“It had to be contained to be produced at the court therefore you couldn’t afford to have it waved around for everyone to see it because it could have got interfered with.”

The Crown Office acknowledged that the fragment had travelled to Germany in 1990, and claimed that “at no time during the investigation was the timer fragment ever outside the custody and control of the Scottish police officers, or forensic scientists at the Royal Armament Research and Development Establishment.”

However, they did not address the break in the chain of evidence or make any reference to the fragment’s travel to the United States, or challenge Grahame's contention that the evidence log is incomplete.

Former Lord Advoate Lord Fraser also stated that as far as he was aware, the evidence had never left the UK.

“The Crown Office have confirmed to me that the fragment, PT-35, the piece of evidence that it was claimed by prosecutors linked Libya to the attack was also sent to Germany in April 1990 as well as the US,” Grahame says.

“On the 22nd of June 1990 it was then taken to the FBI lab in Washington for examination by FBI officials there. Lord Fraser makes it clear he did not know and would not have allowed this evidence to be taken out of Scottish jurisdiction and control, but that is precisely what did happen. That leaves a very serious question mark over the central piece of evidence used to convict Mr Megrahi."