The prison seen in the film is actually a combination of three filming locations: the exteriors are that of the Meaux prison, some 40 kilometers east of Paris, the entrance corridors are part of the Bibliothèque nationale de France in Paris and the other interiors (the cell, the visiting room) are studio sets.
Fred Cavayé and Guillaume Lemans didn't do an enormous amount of research as they didn't want the audience to forget that the hero in an ordinary person, an amateur, who doesn't really know how to proceed.
Diane Kruger insisted on meeting with Fred Cavayé before accepting the part, as she felt that the character of Lisa wasn't fleshed out enough. As such, Kruger and Cavayé spent several months developing the character which had a significantly smaller role in the original draft.
All the prison scenes and the studio interiors were shot in chronological order as Fred Cavayé felt it would be important for the actors and the evolution of their characters.
The opening passages of this remake are almost identical in the US remake, The Next Three Days (2010).