A lawyer acting for the family of murdered Frenchwoman Sophie Toscan du Plantier said the revelation that interviews with witnesses involved in the Ian Bailey case were recorded could be of major interest to the French inquiry.
Alain Spilliaert said it was an opportunity for a new and complete review of the case.
French investigators are due to return to Ireland in the coming weeks to conclude their interviews and investigations.
Ms Toscan du Plantier was murdered outside her holiday home in west Cork in December 1996.
Speaking on RTÉ’s News at One, Mr Spilliaert said the family believed that new events could come to light that would be welcomed.
He said their main concern was that the tapes had not been destroyed:
"If these recordings, tapes for example record some phone calls given by Marie Farrell to the garda this should be of major interest.
"Our concern - the family concern - in the last few days was that any evidence, any new material should be preserved and kept for the French inquiry.
"I understand the Attorney General has instructed to preserve this material and this is quite important for us.
Yesterday, it was reported that gardaí recorded conversations with two main witnesses during the investigation.
Recordings were made between gardaí and Marie Farrell, a shopkeeper in Schull, west Cork and between gardaí and Martin Graham who was an acquaintance of Mr Bailey.
Sinn Féin's Justice spokesperson Pádraig Mac Lochlainn has said Minister for Justice Alan Shatter should clarify his knowledge of Mr Bailey’s case going back to November 2011 up to Monday and Tuesday of last week.
He said the Attorney General should also make a statement clarifying her involvement in this matter since last November.