Dublin footballer Cormac Costello has been found guilty of assaulting another player while he was a spectator at a match.

Costello, a seven-time All-Ireland winner, struck Aodan Fee in the aftermath of a sideline incident during a club encounter between Naomh Mearnóg and Whitehall Colmcille in Portmarnock in 2019.

Fee ended up with a broken tooth and mouth injuries, describing in court how "he had never been struck as hard before".

While Costello claimed to have acted in self-defence in order to extricate himself from the sideline fracas, Judge John King described his use of force as "not reasonable".

"It was a reaction. It was an overreaction and he should have known better," he added.

Judge King ordered Costello, of Lorcan Crescent in Santry, to donate €1,000 to a charity of his victim's choice and applied the probation act at the trial at Swords District Court.