Ian Bailey has described the decision to prosecute him in Paris for the murder of Sophie Toscan du Plantier as "a tragedy for the truth".
Mr Bailey (60) was commenting as Ms Toscan du Plantier's son, Pierre Louis Baudey-Vignaud (37), issued an emotional appeal in west Cork for Irish support in the impending Paris trial.
The Manchester-born journalist said he believed he had already been convicted in France, with a bitter extradition battle now looming between Ireland and French judicial authorities.
"It is a most dreadful and frightening position to be in," he said.
Mr Bailey said he was convinced that, once they secure a conviction, French authorities will demand his extradition. A French bid to have him extradited was rejected by the Supreme Court in 2012.
"It is a nightmare - but it has been a nightmare for the past 22 years," he said.
Ms Toscan du Plantier was beaten to death on December 23, 1996, aged 39, after she apparently tried to flee from an intruder at her isolated holiday home at Toormore, west Cork.
She was found just off a laneway to the property, and had suffered horrific injuries.
No one has ever been charged with her murder in Ireland, despite one of the biggest garda investigations ever mounted.
Mr Bailey, who insisted he never met the French woman, has consistently protested his innocence.
He was twice arrested for questioning but released without charge. The DPP ruled out any prosecution against him more than a decade ago.
Mr Bailey has also claimed "sinister" attempts were made to frame him for the crime.
He claimed there were people in authority in Ireland who know he is innocent but are prepared to stay silent while he is convicted in France based on evidence already rejected here.
"These people are prepared to see me convicted and sacrificed to public opinion in France," he said.
Mr Baudey-Vignaud urged support for the Paris trial, which opens in the Criminal High Court next Monday.
"Sophie fought like a lioness against the most atrocious violence there is," he said. "I come back here every year because it is the only way for me to defy this violence and destroy it.
"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."
The trial will take place before three judges and is expected to last at least a week.
Under French law, prosecutions can be taken against individuals not within French jurisdiction and for alleged offences overseas.