Scotland's High Court will begin hearing an appeal on Tuesday against the conviction of a Libyan man found guilty of the 1988 Lockerbie aircraft bombing, the deadliest militant attack in British history.
Pam Am Flight 103 was blown up over the Scottish town of Lockerbie in December 1988 on its journey from London to New York killing 270 people, mostly Americans on their way home for Christmas.
Libyan intelligence officer Abdel Basset Al Megrahi was jailed for life in 2001 after being found guilty of the murder of 243 passengers, 16 crew and 11 residents of Lockerbie who died in the attack. He is the only person to be convicted over the bombing.
Megrahi, who denied involvement, died in Libya in 2012 after being released three years earlier by Scotland's government on compassionate grounds following a diagnosis of terminal cancer.
In March, an independent Scottish review body ruled his family could launch an appeal after concluding there might have been a miscarriage of justice.
A 419-page review report found that new information still pointed towards “Libya, and Mr Megrahi as an operative in 1988 for that state, as being the culprits in the bombing of PA 103”, the review body found.
But it said the failure of prosecutors to disclose that the US government had paid a key witness, as well as questions over the identity of Al Megrahi as the man who bought items packed inside the suitcase that contained the bomb, meant the case should go to appeal.
"Overturning of the verdict for the Megrahi family and many of the families of British victims also supporting the appeal, would vindicate their belief that the governments of the United States and the United Kingdom stand accused of having lived a monumental lie for 31 years," the family's lawyer Aamer Anwar said.
Five judges will hear the appeal including the head of Scotland's judiciary, Lord Justice General Colin Sutherland.
Megrahi first appealed in 2002 but this was rejected by Scotland's High Court. A second appeal was abandoned in 2009 just before his return to Libya.
In 2003, then-Libyan leader Muammar Qaddafi accepted his country's responsibility for the bombing and paid compensation to the victims' families, but did not admit to personally ordering the attack. However, Megrahi's family and some relatives of the Scottish victims have always doubted his guilt.