An English television programme gave a 61-year-old man the idea to put up posters in his locality naming a publican as an alleged paedophile.
Mr Bernard Clyne, Brighton Cottage, Foxrock, told Dublin Circuit Criminal Court he got the idea from watching a programme called The Bill.
He told his counsel, Mr Michael Cush SC (with Mr Micheál O'Higgins), that a lifelong friend had asked him before he died to ensure justice for his son whom he claimed had been sexually abused by the man he named in the posters.
Mr Clyne has pleaded not guilty to harassing the victim between April 2nd and April 21st, 2003, by putting up the posters.
He said he "believed in every word" he wrote in the posters, which, the jury was earlier told, read "Peadophile Perv", and named the publican as the alleged abuser. He had told gardaí he was "not a great speller".
He said he had not told gardaí about what his friend told him regarding the alleged abuse of his son by the publican because, "one, I was not asked, and, two, the boy was too fragile at the time and could not have stood questions from gardaí".
Once gardaí arrested him for putting up the posters, he said, the publican had arrived at his door with a friend of his and shouted abuse at him. Mr Clyne said the man had thrown a bucket of paint at him and on his house.
He denied that his claim about not telling gardaí of the sex abuse allegations was "nonsensical". Had that been his consideration, he would not have taken into account the effect of the posters on the young man, he said.
He said his friend's son was living with him at the time and he put up the posters on a route which he knew he did not take.
He also denied that his claim of violence perpetrated against him by the publican shortly before his arrest in the early hours of April 21st, 2003, was false.
The now 23-year-old son of Mr Clyne's friend, who was allegedly abused by the publican, told defence counsel Mr O'Higgins he had spoken to his father at his death bed about the publican abusing him when he was a child.
He said he had tried to tell his father about three incidents where the man allegedly sexually abused him in his car. His father had refused to believe him and "bashed" him instead. He was bringing charges against the publican over the alleged abuse.