Brian Meehan, 36, was sentenced to life for the June 1996 killing by Dublin's non-jury Special Criminal Court. He was also convicted of 14 drugs and arms offences, for which he was given various sentences to run concurrently, including five 25-year terms.
Miss Guerin, an investigative journalist with the Sunday Independent, was shot six times as she waited at traffic lights on the outskirts of Dublin by the pillion passenger of a motorbike. The panel of three judges accepted evidence that Meehan was the driver of the motorbike.
Last year an accomplice of Meehan's, Paul Ward, was jailed for life for the murder of Miss Guerin.
The court threw out the evidence of a former accomplice of Meehan's, Charles Bowden, who had been granted immunity from prosecution in return for evidence, and put on a witness protection programme. However, it did accept the testimony of another recruit to the controversial scheme, Russell Warren, who followed Miss Guerin in the hours before her killing and gave details of her movements to Meehan over a mobile phone.
Mr Justice Frederick Morris said the court could not be satisfied beyond reasonable doubt that Mr Bowden's evidence was accurate, particularly as he was an accomplice.
The court also rejected evidence given by Bowden's wife, Juliette Bacon, and that of Julian Clohessy, who socialised with the gang. Mr Clohessy said Meehan had told him during a night out that he was at the scene of the Guerin murder, but he had been drinking and was on drugs at the time.
However the court did accept the evidence of Mr Warren, which was supported by a sighting of him using a mobile phone near the court where Miss Guerin appeared shortly before her murder to face charges of motoring offences.Reuse content