When Vercel answers the telephone call with the anonymous woman at his house, he records it on a cassette deck with the phone's second earpiece. Upon ending the call the earpiece has instantly returned to the back of the phone even before he stops the recording.
When Barbara (Fanny Ardant) stands on a bench by a wall to look over at the race track, she sidles left to right. When the scene cuts to the other side of the wall looking at her peering over the wall, she is moving the opposite direction.
When Marie-Christine reads the newspaper and the bell rings, she throws away the newspaper and jumps up. In the next shot she still holds the paper in her hands and throws is it away again.
Before leaving the shop, Barbara hides the pistol near the right end of a shelf with papers. Upon returning she retrieves it from the far left end.
(at around 1h 12 mins) The Citroen DS car of the Paparazzo from "Le Provencal" carries two different plates: on the Back one from Paris (75) and on the front one from the var district (83).
When Marie-Christine's corpse is wheeled out of Vercel's residence, her eyes noticeably open and move.
When Julien Vercel and his lawyer Clément sit in the car together, there is a close up during which a microphone clearly swings to Julien Vercel.