Lawyers for Ian Bailey, who is wanted by French authorities in connection with the murder of Sophie Toscan du Plantier in 1996, have said the French investigation may have been tainted by garda misconduct in the Irish investigation.
The High Court has adjourned extradition proceedings against Mr Bailey after his lawyers said they needed more time to consider the case.
Counsel for Ian Bailey, Ronan Munro, told the High Court there were strong grounds for contesting this extradition.
He said there was evidence of garda misconduct in the original investigation, which may have tainted the French inquiry.
They will also contend that the proceedings are an abuse of process and an unlawful attempt to subvert the decision of the DPP not to prosecute Mr Bailey.
Mr Munro said they would also argue that it was an interference with his constitutional right to liberty.
He said they would be challenging the right of the French authorities to seek the extradition of Mr Bailey for an offence committed outside its jurisdiction.
The case was adjourned until 2 June.
