Ian Bailey described the French determination to prosecute him in Paris for the murder of Sophie Toscan du Plantier as "a tragedy for the truth".
e also claimed there was "a code of omertà" amongst those in authority in Ireland, who know he is innocent but still remain silent.
Mr Bailey (60) was commenting as Sophie's son, Pierre Louis Baudey-Vignaud (37), issued an emotional appeal in west Cork for Irish support for the impending Paris trial.
The Manchester-born journalist said he believed he had already been convicted in Paris - with a bitter extradition battle now looming between Ireland and France.
"It is a most dreadful and frightening position to be in. It is a nightmare - but it has been a nightmare for the past 22 years," he said.
Ms du Plantier (39), a mother of one, was beaten to death on December 23, 1996, after she apparently tried to flee from an intruder at her isolated holiday home at Toormore in west Cork.
No one has ever been charged with her murder in Ireland, despite a major Garda investigation.
Mr Bailey, who insisted he never met the French woman, has consistently protested his innocence.
He was twice arrested by gardaí for questioning, but released without charge on both occasions.
The Director of Public Prosecutions ruled out any prosecution against him.
Mr Bailey also claimed that "sinister" attempts were made to frame him.
"These people are prepared to see me convicted and sacrificed to public opinion in France," he said.
He said it was akin to "a code of omertà", where those who know the truth still refuse to speak out.
Mr Baudey-Vignaud urged support for the Paris trial, which opens before the Criminal High Court on May 27.
"Sophie fought like a lioness against the most atrocious violence there is," he said.
"For 20 years, I have trusted you. Do not betray me. Do not betray yourselves. You know as well as I do who killed my mother."