Article R51 of the French Code of Criminal Procedure
The notification provided for by Article 706-37 is made by registered letter with acknowledgement of receipt. Where it appears from the acknowledgement of receipt that the addressee is unknown at the address indicated, notification is made by the police or gendarmerie services. The copy of the registered letter or the police or gendarmerie report is appended to the proceedings. This information is not given to persons who are themselves the…