The mother of Paul Quinn has appealed for those who know what happened to her son to "tell us the truth" and "clear your conscience".
Mr Quinn, who was from Cullyhanna in south Armagh, was 21 years old when he was lured to a shed near Castleblayney in Monaghan by a group of men.
He was brutally beaten and murdered.
Speaking on the 18th anniversary of his death, his mother, Breege Quinn, appealed for justice and asked people with information to come forward.
"Please, please, tell what you know. Clear your conscience. Even for your own sake. As I said, you don't have to put your name to it, just tell us the truth and help us to get justice and that's all we ask," she said.
Despite the many years that have passed, Ms Quinn said that "it feels like yesterday" since her son died.
Speaking about her son, Ms Quinn said he was "full of life".
"He had a great personality, just like any young lad of 21. He loved going to discos and out at the weekends," she said.
"It doesn't have to be an anniversary to think of what he went through," she said.
"It could mean we could start living a bit of a life again. Our life has been brought to a halt. That's what it would mean to us. We're not getting any younger. The people that done it, they're not getting any younger either."
Ms Quinn said she is in regular contact with gardaí.
"We hope and pray every day that we will get justice," she said.
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23 arrests
So far in the investigation into his murder, a total of 23 people have been arrested on both sides of the border.
This includes 14 people arrested by gardaí and nine people arrested by the Police Service of Northern Ireland.
In March 2020, a thematic review of the investigation was completed by the Garda Serious Crime Review Team.
In a statement marking the 18th anniversary since the death of Mr Quinn, gardaí said solving his murder is of the "utmost priority" for the force and they are continuing to work with the PSNI.
Gardaí believe there are still people out there with information in the community who have yet to come forward and said any information will be treated with absolute confidentiality.
Read more: Paul Quinn's mother appeals for justice on 17th anniversary of murder
Superintendent Ronan Carey said gardaí want to provide answers and justice to Mr Quinn, his mother Breege and his father Stephen.
"We firmly believe that the answers to this murder or the evidence that we require to progress this investigation lies within the community.
"That relationships change or the nature of them, and that people may be in a position now to provide answers to us or come forward to us and give us information that they may not have been previously in a position to do so," Supt Carey said.
Anyone with information can contact Casteblayney Garda Station on 042 9747900 or the Garda Confidential Line on 1800 666 111.
