The first day of Ian Bailey's Supreme Court appeal against his extradition to France has concluded.
The High Court ordered Mr Bailey's extradition last year.
French authorities want to question him about the murder of French film producer Sophie Toscan du Plantier at her holiday home in Schull, Co Cork in 1996.
Mr Bailey has always denied any involvement in the killing.
In court today, Mr Bailey's lawyer Garrett Simons SC questioned the right of French legal system to exercise authority over this case in Ireland.
Mr Simons submitted that the State was not required to extradite in a case where if reversed, Ireland would not have the right to do the same.
He said Irish law on this area centred on the citizenship of the accused whereas French law centred on the citizenship of the victim. Therefore he said, there is no reciprocity and an accused cannot be extradited.
Mr Justice Niall Fennelly questioned whether the citizenship of the offence constituted an element of the offence.
Mr Bailey's lawyers also say that documents they received from the State last November show that the French request to extradite Mr Bailey is tainted because of the way the Garda investigation into Ms Toscan du Plantier's murder was conducted.
The documents were described by Attorney General Máire Whelan in correspondence as "very significant".
They include a document from former DPP Eamonn Barnes, who was director when the decision was taken not to prosecute Mr Bailey for the murder.
He described the garda investigation in relation to Mr Bailey as thoroughly flawed and prejudiced.
The State has argued there is nothing new in the arguments being made by Mr Bailey's legal team and the new documents are irrelevant to the extradition case.
The hearing is expected to last three days.
