The High Court has granted an order giving Ian Bailey access to more documents relating to the garda investigation of the 1996 murder of Sophie Toscan du Plantier.
Mr Justice Hedigan said the background to the case could only be described as "disturbing".
The court heard further detail of documents in which the garda investigation was described as "thoroughly flawed and prejudiced".
An email from former director of public prosecutions Eamonn Barnes also revealed he believed gardaí engaged in "grossly improper attempts to achieve or even force a prosecutorial decision" against Mr Bailey.
The documents first came to light on the eve of Mr Bailey's Supreme Court appeal against his extradition to France, where he was wanted by authorities in connection with the murder of the French film maker in Cork.
He successfully appealed the decision of the High Court to extradite him.
More details of the content of the documents were presented to the High Court.
Mr Bailey's lawyers say the content would indicate the existence of further documents, which they say are highly relevant to his case against the gardaí for malicious prosecution and false imprisonment.
They asked the High Court to order disclosure of a wide range of records relating to Mr Bailey, including any contact between gardaí and former and current DPPs.
The court heard an email from Mr Barnes details a meeting with State solicitor in west Cork, Malachy Boohig, in which Mr Boohig told him senior gardaí asked him to use his connection with then minister for justice John O'Donoghue to put pressure on the DPP to order Mr Bailey be charged with murder.
Mr Barnes refers to his awareness of the "anxiety of gardaí to charge Bailey and not just the gardaí in west Cork, strong and persistent advocacy having been deployed by them on the [DPP's] office for some considerable time".
Mr Bailey was never charged with the murder of Ms du Plantier and has always claimed he is innocent.
Senior Counsel Martin Giblin told the court it was "beyond doubt" there were persons in the employ of the State who were until very late in the extradition proceedings contemplating not disclosing this material.
Lawyers for the State had objected to the disclosure of the documents, saying it was a "fishing" exercise and some categories of documents sought were irrelevant.
Senior Counsel Paul O'Higgins said he needed to point out to the court there was nothing illegal about advocating a prosecution to the DPP.
Mr Justice Hedigan said he would be more liberal than usual in this case due to the "disturbing" background outlined to the court today.