A Dominican priest and former headmaster has been sentenced to three years in prison for the multiple sexual assaults of a boy over an eight-year period.

Fr Vincent Mercer, 66, pleaded guilty at Cork Circuit Criminal Court to 15 sample counts of sexually assaulting the boy on various dates between 1986 and 1994.

The priest is out of ministry, but remains a member of the Dominican Order. He is also a former headmaster of Newbridge College in Co Kildare.

The victim was aged between 11 and 17 at the time and the abuse happened when Mercer resided at St Mary's Dominican Church at Pope's Quay in Cork.

Judge Seán Ó Donnabháin described the abuse as the most serious breach of trust given the priest's occupation, his age and the boy's age and that he was a family friend.

He sentenced Mercer to three years, with the final 18 months suspended.

Judge Ó Donnabháin noted the abuse went on for a long period of time and increased in severity over time.

Earlier, the victim told the court he was vulnerable and an easy target, too frightened to reveal what was happening to him for fear of not being believed.

He said that Monday 6 May 2012, when he broke his silence, was the first day of the rest of his life.

The victim said he could no longer live with the devastation he was feeling, he had to speak out and reveal the abuse he had suffered.

He told the judge he was in court for one thing: justice. He said he wanted justice for what Mercer did to him and his family over the last 27 years.

Mercer apologised to his victim, saying he was truly sorry for the terrible hurt and trauma he caused and the impact on his victim's life.

In 2005, Mercer was convicted of indecently assaulting eight boys in his care aged between ten and 13 years on various dates between 1970 and 1977.

At the time, he received a suspended three-year sentence at Naas Circuit Criminal Court.