The State has been ordered to hand over a raft of documents to Ian Bailey, the man twice arrested over the death of Sophie Toscan du Plantier.
Ian Bailey was arrested in 1996 and 1997 for questioning over the killing of the French film producer at her holiday home in Schull in 1996.
He believes the new material will support his High Court claim of malice against him during the Garda probe into the murder.
He alleges there was a concerted and calculated campaign to falsely and deliberately establish that he was responsible for this heinous crime.
He is now suing the gardaí and the State for millions in compensation.