I saw that movie around summer of 1974. I was only 12 !
The movie was called "Two against the law", Gabin/Delon. It was against Capital Punishment and how one mistake can take you to a fateful destiny, how the society does not give some a second chance.
The movie was good, makes you think on the other side of things. But the music was amazing - beautiful beyond belief - the Theme music by Philippe Sarde is just unbelievable.
I have not heard the soundtrack for 36 years - yet I have always caught myself playing it on the piano, humming it to myself - or simply playing it in my head - in so many occasions ... 36 years have passed ... yet I remembered each key and track and variation (as the theme was played in several variations within the movie - I still remember the scene of the flowing water ) ...