Ian Bailey claims the 'real murderer' of Sophie Toscan du Plantier died a long time ago.
The former journalist is calling for a cold case review of the crime, which he claims would clear him.
The French film-maker was murdered in west Cork almost 25 years ago.
Last week her son, Pierre-Louis Baudey-Vignaud, called for the Director of Public Prosecutions (DPP) to put Mr Bailey on trial here.
Responding to this, Mr Bailey told Newstalk: "I'm very, very sorry for the pain and suffering that Pierre-Louis and the family have gone through.
"But to hold me as the person responsible is just ridiculous at this stage.
"I just think it's really sad for everybody... and it's all based on a dirty, rotten stinking lie from day one that I'm somehow connected to this crime.
"It's 25 years on and it's exacting its toll on a lot of people".
And he believes he knows who really killed Ms du Plantier.
"Somebody in Ireland knows that it wasn't me - I don't know if anybody does know who is was, I suspect there are people who do know who it was.
"Is the killer still alive? I keep seeing this reference, the fact that the killer I think - if my own theory is correct, and I can't say too much about it - the murderer is dead and has quite a long time ago passed away.
"I don't absolutely 100% know... my belief is that the murderer is probably dead - but that's a belief, I can't prove that".
Mr Bailey wants the Garda Commissioner Drew Harris to order a cold case review of the crime.
"There were two salient facts I drew to the attention of Drew Harris.
"One was the fact that there was apparently alien blood - when I say 'alien blood' not the victims blood - found upon her shoe, clearly not my blood because they have my blood samples from very early on.
"And then you have the situation, as we now know, evidence going missing like the six-bar gate.
"Then you have statements that would have exonerated me that have gone missing".
He says he has written to Commissioner Harris three times with this request, but has yet to receive a promise of a cold case review.
"My big prayer has been for a long time that the truth comes out and the truth be acknowledged that I have nothing to do with this.
"I've written to Drew Harris relatively recently asking for a cold case review.
"I haven't heard back, I believe that's being considered but it hasn't been confirmed yet.
"And I do all I can at every level to fight my corner, as an innocent person would".
On a recent visit to Ireland, French President Emmanuel Macron offered him a new trial if he agreed to go to Paris.
Mr Bailey says this will not happen.
"I think he was very misinformed about the Irish legal system - he sort of indicated that there were ongoing talks about the possibility of me being extradited.
"That's been settled [in] three court cases.
"I thought those comments were rather misplaced... what do they think I'm going to do: hand myself over knowing that I will not get a fair trial?
"There's a word in French - it's Arabic word maboul - it means like loco, like mad.
"And it's a crazy suggestion that I should hand myself over to the French Republic".
Additional reporting: Jack Quann