A man who beat a grandfather with a dumbbell and stamped on his head and chest has received a mandatory life sentence for his murder.

Joe O'Brien, 60, of Spring Garden Alley in Waterford, died after he was attacked by three people in an apartment at Scotch Marsh, William Street, on 23 April 2012.

Waterford man Patrick Keating, 49, started a mandatory life sentence this evening for murdering the father-of-two and grandfather, who was beaten during a drinking party in the city last year.

However, the sentence was back-dated to the date of the offence.

During the seven-day trial, the jury heard how Keating, in custody since his arrest over the murder, hit Mr O’Brien with a dumbbell and stamped on his head as he begged "please don't hit me again".

Keating, of Moyne House at Grattan Quay in the city, was found guilty of murder after two hours of deliberations at the Central Criminal Court in the city.

Two women have pleaded guilty to unlawfully killing Mr O'Brien.

They will be sentenced in December.