When Madeleine is putting on her dress after getting her wounds clean, she slips her arm into the sleeve twice.
When guillotining someone, a wooden piece called a lunette is placed above the neck so the condemned can't move it. No lunette was used in the opening scene.
Numerous inaccuracies regarding chronology and biography. The opening narrative does explain that the facts have been "tarted up."
When Simone is buying her copy of "Justine", the date visible on the cover is MDCCCCVII: 1907. There is one C too many.