IAN Bailey's partner Jules Thomas is to seek an order in the High Court today looking for discovery of documents.
They relate to her arrest by gardai more than a decade ago.
Ms Thomas was arrested in February 1997 and in 2000.
Gardai were investigating the murder of French woman Sophie Toscan du Plantier (inset) in Cork in 1996.
Ms Du Plantier's was found bludgeoned to death outside her west Cork holiday home in December that year.
In confidential correspondence at the time, the Director of Public Prosecutions claimed that the arrest was unlawful according to documents which were recently released by the State as part of a separate court case.
Ms Thomas is believed to be seeking all documents relating to emails between two former Directors of Public Prosecutions, James Hamilton and Eamon Barnes, in which the men discuss a confidential report into her and Mr Bailey's arrests.
Mr Barnes, who retired as DPP in 1999, believed that gardai had acted inappropriately in trying to influence his office to bring charges against Mr Bailey.
Mr Bailey, who was twice arrested for questioning in relation to the killing but never charged, has always protested his innocence.