Ian Bailey says he's frightened for his safety after receiving death threats over Sophie Toscan du Plantier's murder.
The self-confessed suspect has spoken out ahead of the 25th anniversary of the west Cork crime.
French film-maker Sophie Toscan du Plantier was killed with a rock and a concrete block on December 23rd 1996, outside her holiday home in Schull in west Cork.
At first, journalist Ian Bailey reported on the murder but was then arrested twice in connection with it, although he was never charged here.
He says being a suspect has ruined his life - and has led to him receiving death threats, including several on Twitter.
Speaking to Newstalk, Mr Bailey outlined one he received last month.
He said: "On November 1st at midnight, he said 'when I see you, I'll do to you what you done to Sophie'.
"This guy could turn up... he sounds like a psychopath to me. I have to be quite careful about my own personal security, and when I'm out I'll have my back covered."
He said he has also received "threatening phone calls from unknown people".
'No intention' of going to France
Mr Bailey denies any role in Sophie's death, but he was found guilty of her murder in his absence in a Paris court two years ago.
However, the French have failed to get him extradited - and the country's president, Emmanuel Macron, has offered him a new trial if he agrees to travel there.
Mr Bailey said: "I have no intention of going over there - their system of law will find me guilty."
Mr Bailey is calling on the gardai to carry out a cold-case review into the unsolved crime.
He says has written to Garda Commissioner Drew Harris with that request.
Mr Bailey also spoke of his regret at assaulting his former partner, Jules Thomas, several years ago.
He said: "We had had sort of fights... domestic problems.
"That was used as an excuse against me, that I had these two incidents.
"We had both been drunk, but that's no defence - it was to my eternal shame."