Christopher Slator (37) had denied Mr Barr's murder and his lawyers argued that the prosecution had failed to prove that there was no innocent explanation for how his DNA ended up on the mask and runners.
The three-judge, non-jury court today rejected their arguments, saying there is no rational explanation for his DNA being on those items other than that he is guilty of murder.
The court also found that Slator fled the jurisdiction the following day by booking flights to Dubai with Eamon Cumberton, who has previously been convicted of Mr Barr's murder.
The two men returned to Ireland together about one month later. Ms Justice Tara Burns said the flight was "extremely unusual" given that it was booked three hours ahead of departure and neither Cumberton nor Slator had any luggage or even a backpack or rucksack.
She said the DNA evidence alone was enough to convict Slator but the "highly suspicious" flight provides further support for the conviction.
On the night of April 25, 2016, father-of-five Mr Barr was socialising at the pub, where he was a manager, when he was shot seven times - five times in the head. Two armed males had burst in wearing what were described as 'Freddy Krueger', or Hallowe'en style masks.
The trial heard there was "chaos and screaming" in the aftermath of the gun murder, which took place during a raffle for the families of Republican prisoners.
Slator will be sentenced to the mandatory term of life imprisonment later today.
Slator of Carnlough Road, Cabra, Dublin 7, had pleaded not guilty to the murder of Mr Barr at the Sunset House pub on Summerhill Parade in Dublin 1 on April 25, 2016. He is the third man to go on trial in relation to the murder.
In November 2020, David Hunter (43) of Du Cane Road, White City, London, was also jailed for life for the murder of Mr Barr. Eamon Cumberton, of Mountjoy Street, Dublin 7 was jailed for life for the murder in 2019.
A fourth man, Martin Aylmer (36) of Casino Park, Marino, Dublin 3 was sentenced to a little under four years after he pleaded guilty to buying mobile phones for the gang who murdered Mr Barr. His sentence was later increased to six years by the Court of Appeal.