SCOTTISH police had information that might have changed the outcome of the Lockerbie bombing trial, a BBC TV programme has learned.
The information could have affected the credibility of key evidence, but was not passed to the defence team.
Libyan national Abdelbaset ali Mohmed al-Megrahi is serving life for killing 270 people in the 1988 bombing.
A prosecution witness had seen a picture linking Megrahi to the bombing before he identified him.
Megrahi, 56, who maintains he is the victim of a miscarriage of justice, has been granted leave to appeal against his conviction for a second time.
One significant reason for the appeal is that Tony Gauci, who picked Megrahi out in a line-up, had looked at a magazine photograph of him just four days before he made the identification.
The Conspiracy Files: Lockerbie has now seen documentary evidence that Scottish police knew this was the case.
That information should have been passed to the defence, but the disclosure did not take place.
In the same programme, Saif al-Islam al-Gaddafi, the son of Libyan leader Colonel Muammar al-Gaddafi, has called the families of the 1988 Lockerbie air disaster "greedy" and "materialistic".
Megrahi was convicted of the murders on 31 January, 2001 after a lengthy investigation by the Scottish police and the FBI, and a nine-month trial at a specially convened Scottish court sitting in the Netherlands.
The Conspiracy Files: Lockerbie is on BBC 2 on Sunday at 9pm.