A 78-year-old serial child sex abuser has been sentenced to ten years in jail for repeated rape and sexual assault of a 13-year-old boy.

Patrick O'Brien had pleaded guilty at the Central Criminal Court to 15 charges, including rape and sexual assault.

He also admitted three counts of committing acts of gross indecency.

The former Church of Ireland lay worker is currently serving a 13-year sentence for previous offences against 14 boys.

The victim in this case had first made allegations against O'Brien in 2002 but nothing was done.

He withdrew his statement eight years later and no prosecution took place until the case was revisited in 2016.

Mr Justice Butler described the abuse as persistent and appalling. He said a harrowing victim impact report showed the abuse had a profound effect on the victim.

The judge said it was very difficult to sentence a man of this age and suggested that the Irish Penal Reform Trust should carry out a study on the sentencing of elderly people.

The offending took place at O'Brien's home at Knocklyon Road, Templeogue, Dublin and other locations in the city on dates between April 2002 and December 2003.

O'Brien is currently serving a 13-year jail term imposed in 2016 after he pleaded guilty to the rape and molestation of 14 young boys over the course of 40 years.

In 1989, he received a suspended sentence for the sexual assault of a ten-year-old boy in 1982.

The court heard that the victim in this case was confused about his sexuality at the time and had met a man 20 years older than him. This man, who is before the courts, introduced the victim to O'Brien and brought him to his house in Templeogue.

The victim said the sexual activity with O'Brien changed his idea of normality. He said he felt it was normal at the time but later realised it wasn't.

"I felt degraded and dirty," he said.

Sean Guerin SC, defending, told the court that his client had attended hundreds of hours of therapy and group therapy while in custody at Arbour Hill prison.

O'Brien also participates in Sunday services as a choir singer and assists in a prison education programme.

He said he will be in prison until the age of 87. He said there was no offending for a period after O'Brien's conviction in 1989 and this demonstrated O'Brien's capability for rehabilitation.

The court also heard that in 2008 a relative of the victim demanded money from O'Brien to stay quiet about his offending. O'Brien paid this man a large sum of money and the man was later investigated for blackmail.

The victim first made allegations against O'Brien in 2002. Anne Rowland, prosecuting, told the court that "inexplicably nothing seems to have taken place" with the investigation at the time and this has "never being explained satisfactorily".

In around 2010, gardaí again approached the complainant who made a statement withdrawing the complaint. A file was sent to the DPP but because of the victim's withdrawal statement, no prosecution was brought.

Inspector Barry Walsh agreed with Mr Guerin that it was on the advice of a former colleague of his that the complainant decided not to pursue charges.

The court heard the victim felt he might be held responsible because he had accepted gifts from O'Brien during the abuse.

Insp Walsh told the court that when he came into the case in 2016, he met the victim and advised him that as a minor at the time of the offending he was under the age of consent.

A second file was sent to the DPP and prosecution followed.

After his arrest O'Brien asked to hear the victim's allegations and then told gardaí: "I accept the main content of what he said and I am very sorry."

Mr Justice Butler said that O'Brien was a repeat offender and that society is entitled to expect that offenders will be punished for all offending.

He noted the accused has apologised for these offences.