Jock Thomson QC, who became Queen's Counsel in 2000, is understood to have passed away on Monday.
The lawyer, and ex-police officer, was admitted to the Scottish Bar in 1983. He went on to work as a senior depute procurator-fiscal in Glasgow and also as a defence lawyer.
Latterly, he was an outspoken critic of the Crown Office and the move towards abolishing corroboration, saying it would be a "draconian step".
Banny Mackinnon, practice manager at Mackinnon Advocates - of which Mr Thomson was a member - said: "We are all very sad at Jock's passing.
"He was a much-loved and respected member of our Stable and will be sorely missed, not just by our own members, but by many others in the Faculty and indeed in the legal world and beyond."
Mr Thomson, a fan of opera and whose wife Christina is a soprano, became a member of the Justice for Megrahi campaign last year, set up to lobby for the conviction of the Lockerbie bomber to be re-examined.
Robert Forrester, of the Justice for Megrahi campaign, said: "Jock was one of life's good guys. He was one of the most highly principled and open individuals I have ever had the honour of encountering."