Bresson insisted on complete authenticity. Original author Andre Devigny served as adviser on the film, which was actually shot in the same Montluc prison where he was incarcerated. Devigny also loaned Bresson the ropes and hooks he had used in his escape.
When the film was shot, the Montluc prison was still an operating prison. The prisoners had to be evacuated to other facilities for two weeks during the shooting of the film on location. The prison was definitively closed in 2009. It is now a memorial.