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The 270 people who lost their lives in the Lockerbie bombing exactly 26 years ago will be remembered at a memorial service in the United States today.
Leading the delegation will be Scotland's top prosecutor, Lord Advocate Frank Mulholland.
He has reaffirmed his belief in the guilt of the only man convicted of the bombing, Abdelbaset al-Megrahi, and vowed to track down his accomplices.
Mr Mulholland said no Crown Office investigator or prosecutor has raised a concern about the evidence in the bombing of Pan Am flight 103 over the south of Scotland on December 21 1988.
Megrahi's part in the bombing of the flight from from London to New York has been called into question in a series of books and documentaries.
A petition seeking ''Justice For Megrahi'', backed by politicians and family members of some UK victims, remains on Holyrood's books more than two years after Megrahi's death.
Addressing the memorial service later, Mr Mulholland will tell the gathering his investigation ''remains on the evidence, and not on speculation and supposition''.
He will say: ``The current instability in Libya has meant that some investigative opportunities have required to be reassessed, which I know has been frustrating for family members.
''However our prosecutors and police officers, working with UK Government and US colleagues, will continue to pursue this investigation, with the sole aim of bringing those who acted along with Al Megrahi to justice.
''There are other significant investigative opportunities open to us which are not reliant on obtaining evidence from our Libyan colleagues.
''The Crown will never give up the fight to secure justice for the families of those who died.
''It might be 26 years since 270 people lost their lives in the terrorist attack but justice has no sell-by date in Scotland.
''Over the years many people have worked on the inquiry and all have been given the same instruction; to carefully review the evidence and work to identify all of those who were involved in the conspiracy to destroy Pan Am flight 103.
''During the 26-year long inquiry not one Crown Office investigator or prosecutor has raised a concern about the evidence in this case.
''We remain committed to this investigation and our focus remains on the evidence, and not on speculation and supposition.''
Earlier this year, Megrahi's relatives embarked on a legal bid to clear his name amid claims that his case is the ''worst miscarriage of justice in British legal history''.
Six immediate members of his family joined forces with 24 British relatives of those who died in the atrocity to seek, ultimately, a third appeal against his conviction in the Scottish courts.
They united to submit an application to the Scottish Criminal Cases Review Commission (SCCRC) for a review of the conviction, a move which could see the case referred back to the High Court.
One of those British relatives, Jim Swire, whose 23-year-old daughter Flora died in the bombing, has expressed his disappointment at Mr Mulholland's latest comments.
Dr Swire told Sky News: ''For the Lord Advocate to say there isn't a shred of evidence to suggest that the trial was anything other than what it should have been is analogous with the late Mandy Rice-Davies when she says 'he would say that, wouldn't he'.''
He added that Mr Mulholland ``wasn't around at the time of Lockerbie, whereas I was, unfortunately''.
''Twenty-six years ago is a long time and I suppose he means people currently in his Crown Office don't believe there is anything wrong with the evidence.
''But I think if you open your eyes and look you cannot fail to see that there is a problem.
''More importantly than that, Scotland's own Criminal Cases Review Commission years ago found six reasons why this case should be revisited and reviewed.
''So for the Lord Advocate now to say there isn't a shred of evidence flies in the face of what the Scottish Criminal Cases Review Commission actually told the world years ago.''
The 259 people on the plane and 11 Lockerbie residents died when the aircraft exploded over Scotland.
Megrahi was jailed for life and lost his first appeal against the mass murder conviction in 2002.
An investigation by the SCCRC led to a finding in 2007 of six grounds where it believed a miscarriage of justice may have occurred, paving the way for a second appeal.
But the Libyan dropped that appeal in 2009 before being released from jail by the Scottish Government on compassionate grounds in light of his terminal prostate cancer.
He died protesting his innocence in Libya in 2012.