Le Septième Juré is an adaptation of Francis Didelot's novel of the same name (1958). A film of the same name was also made by Georges Lautner in 1962, set in Pontarlier, Doubs.
Grégoire Duval (Jean-Pierre Darroussin) is a chemist who lives with his wife Geneviève (Isabelle Habiague) in provincial France and then one day, while fishing and in a moment of insanity strangles a young woman in a barn. This matter occurs at the end of the Algerian war and many French people are racist, which provides a suitable occasion for the Algerian Khader Boualam (Lahcen Razzougui), the woman's last lover, to be tried for the murder: he is just the scapegoat France needs.
But Grégoire is on the jury and tries his best to point out inconsistencies in the trial: he is wracked with guilt that an innocent person possibly faces the death sentence and he has sleepless nights. He tells his wife the truth but she swears him to a vow of silence because Grégoire's being found guilty would destroy them.
In the end Grégoire can't live with himself, hangs himself in the same barn, and leaves a confession of two murders which are promptly destroyed. So much for justice.