Three of Scotland's most senior judges said Mr Mackie had suffered a miscarriage of justice.
Mr Mackie, of the Edinburgh stockbrokers Bell Lawrie White, said afterwards: 'I'm very pleased. It's been two and a half years, which is a ridiculous length of time for me to prove my innocence. I am annoyed at the way certain parties have behaved, but I am not bearing any grudges.
'I am very grateful for the support I've had from my colleagues at Bell Lawrie White and from the companies I follow as an analyst. Not one of them has said they would not talk to me in the future.
'Even my competitors have been supportive. They have not said 'sod Mackie, he's out of the game, let's take the business'. I am looking forward to getting back to speaking to clients again. That's my job.'
His conviction had shocked the financial community. He was regarded as thoroughly respectable and many analysts felt they would have done the same thing in similar circumstances.
The case dated back to September 1991, when Bell Lawrie clients sold about 2 million shares in Shanks & McEwan, a waste disposal and construction company. The sale followed advice from Mr Mackie after he had attended a meeting with Peter Runciman, chairman of Shanks & McEwan.
After the shares were sold for pounds 5.7m the company issued a profit warning, hitting the share price.
Mr Runciman said he had told Mr Mackie of the impending profit warning. This would have made Mr Mackie an insider, unable to advise on dealings in the company's shares. However, he denied he was told of the warning. He said Mr Runciman informed him it was never going to be a vintage year and there would not be much growth in earnings per share. This information was not confidential and Mr Mackie said he had been entitled to warn clients to reduce their holdings.
A jury found Mr Mackie guilty by a majority and the judge, Robin McEwan QC, fined him pounds 25,000. Mr Mackie appealed.
Yesterday Scotland's top judge, Lord Justice General Hope, and Lords Cowie and Mayfield said that although the jury accepted Mr Runciman's evidence as reliable and credible, under Scottish law it still had to be corroborated.
Lord Justice General Hope said: 'In my opinion, the facts and circumstances were entirely consistent with the innocent account which the appellant gave of his meeting with Mr Runciman. They were not capable of corroborating the account of it which Mr Runciman gave in his evidence.
'In my opinion there was a miscarriage of justice in this case because there was insufficient evidence in law for a conviction.'
The case had stemmed from a joint investigation by the London Stock Exchange and the Department of Trade and Industry.
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