A French magistrate hopes to conclude an eight-year investigation into the Sophie Toscan du Plantier murder within weeks, with a Paris court to decide early next year about a prosecution over her killing.
The revelation came as an elite team of French detectives arrived in Ireland to conduct final interviews for Magistrate Patrick Gachon.
Around 15 interviews are now expected to be conducted in Dublin and west Cork into the brutal 1996 killing.
Sophie's brother, Bertrand Bouniol, and her son, Pierre-Louis Bauday, vowed their fight for justice will never stop.
"Magistrate Gachon has a large file, a big folder on all work done over the past eight years. But he wants more answers to some questions," Mr Bouniol said.
"That is why he has sent French police to Ireland to add more answers to his questions."
The French police team arrived in Ireland after the Government sanctioned the visit, which had been delayed for two years because of Ian Bailey's High Court civil action against the State.
Mr Bailey (58), who has consistently protested his innocence in relation to the matter, claimed he was wrongfully arrested by Gardai as part of their 19-year probe into the murder of Mrs du Plantier. Following protests from the legal team representing the Manchester-born freelance journalist, the Department of Justice suspended all co-operation in 2013 with the French authorities over their probe.
The suspension was lifted last summer after the High Court rejected Mr Bailey's wrongful arrest claim following a marathon trial.
He is appealing that ruling to the Supreme Court. Papers in respect of his appeal will be lodged this week.
The Paris detectives plan to conduct around 15 further interviews in Ireland on the instructions of Magistrate Gachon.
The 39-year-old mother-of-one was found battered to death on a laneway leading to her isolated holiday home at Toormore outside Schull in West Cork two days before Christmas.
No-one has ever been charged with her brutal killing.
Magistrate Gachon required the permission of the Irish authorities to allow his team to conduct a final round of interviews.
His detectives conducted a seven-hour interview with Mr Bailey's partner, Welsh artist Jules Thomas, in 2011. However, the French investigation has been frustrated by the death of a number of the original garda witnesses since 1996.
But Sophie's son, Pierre-Louis Bauday (34), has vowed he will never rest until a prosecution takes place over his mother's death. Mr Bauday, who called his first daughter 'Sophie' in honour of his mother, now owns Sophie's holiday cottage.
Mr Bailey has repeatedly predicted that the French will attempt to try him in absentia.
He successfully fought a French attempt to have him extradited, with the Supreme Court unanimously throwing out the European Arrest Warrant application three years ago.
The Gachon inquiry was launched following repeated pleas from Sophie's family after they learned no prosecution was contemplated in Ireland.
The investigation has included the exhumation of Sophie's body, a battery of new DNA and forensic tests as well as the re-interviewing in Ireland of all the witnesses in the original garda probe.
Magistrate Gachon will make a recommendation about a French trial process in January.
That will later go to the Court d'Accusation, which will then have to ratify any trial in absentia before the Court d'Assizes in Paris.