This is a film that belongs in the "Spaghetti Gangster" category. If it had been subtitled instead of dubbed it probably would have played in arthouses instead of grindhouses. There are some moments that don't really play to an American audience (such as the one in which the titular 'Smiling Maniacs' beat and rape Fernando Rey's mistress, a scene that swings schizophrenically back and forth between slapstick and ugly realism), but for the most part this is a pretty sturdy, involving drama of "corruption in the palace of justice".
Review of Smiling Maniacs
