Real police officers were highly offended by how their police counterparts were portrayed in the movie. During the Cannes film festival premiere, they 'greeted' the arriving cast and crew by turning their backs to them in protest. Despite their efforts, the movie received a standing ovation from the crowd afterward.
The film was originally filmed in color but changed to b/w in post-production by Mathieu Kassovitz himself. A color re-release was planned in case the original release failed at the box office.
At one point, Julie Mauduech (one of the girls at the gallery) says to Hubert Koundé, "We've met before, haven't we?" which might be a reference to Mathieu Kassovitz's first film, Métisse (1993), in which they both starred.
The DJ who appears in the upstairs project window and scratches with Cut Killer's "Nique la Police" is actually Cut Killer himself.