Mr McGahon has claimed Sinn Féin was involved in a cover up after he was sexually abused by a member of the IRA
A man who alleges to have been raped by an IRA member says he believes Gerry Adams is lying about his knowledge of the murder of Brian Stack.
Paudie McGahon claims he knows from personal experience that Sinn Féin does not tell the truth about criminal investigations.
The ongoing controversy surrounding Gerry Adams, the Sinn Féin party and the Stack family has proven a major political talking point this week.
Brian Stack, chief prison officer at Portlaoise Prison, was shot by the IRA in 1983 and died 18 months later.
Mr Stack's son Austin has claimed the Sinn Féin leader has information that is crucial to the investigation of his father's murder.
Deputy Adams gave a public statement in the Dáil on Wednesday evening, and yesterday 'rejected absolutely' any allegations that he had told lies or untruths.
The situation has reverberations for Paudie McGahon, who has publicly alleged that he experienced sexual abuse at the hands of an IRA member in the 1980s, participation in a IRA kangaroo court, and subsequent disassociation by the Sinn Féin party.
He spoke to Newstalk Breakfast this morning about the current controversy, saying 'without doubt' that he believes Austin Stack.
"[I'm] 100% behind the Stack family, and Austin, and his brother," he explained. "I just think he's an incredible witness [...] He has the neck to do it, and fair play to him."
He told Paul about his own experiences and the associated Garda investigation. He explained his life is 'up and down'.
"I have a good wife, and three lovely children, and that keeps me stable," he said. "But when you walk the streets or go for a sociable drink, and we'll say members or friends of Sinn Féin are hurling abuse at you - vile, vile comments [...] You sit there and you have to take this abuse, because you went public and you don't go public without expecting some abuse. I take what I can.
"I have people that I know are members of Sinn Féin and they're 100% behind me. But you have the vile ones who will hurl abuse at you."
Returning to the Stack controversy, he argued: "[When I saw] Gerry Adams' speech... only that I love the TV I have in the living room I would have kicked the TV in. But they have absolutely no respect for the general public. 'Push it under the carpet, this will go away'. If Gerry Adams was to jump into a slurry put, he'd jump out smelling of roses."
He concluded by urging Austin Stack to keep going.
"It's hard. It's not easy. I had some tough times over the last 18 months. I shed enough tears. But as I said I grew a bigger backbone than I had.
"I would say to Austin: tiocfaidh ár lá lad, our day will come."