The Bloodstained Butterfly (1971)

While walking through a park in a rainy day, the young Françoise Pigaut is stabbed to death by man wearing raincoat and hat. Inspector Berardi is assigned to investigate the case and soon the TV anchor Alessandro Marchi becomes the prime suspect. His daughter Sarah Marchi was Françoise's best friend and their common friend Giorgio had a crush on Françoise. Alessandro's friend and attorney Giulio Cordaro defends him in the court but Alessandro is found guilty and sent to prison. When two other women are murdered and it is found that Alessandro's wife Maria Marchi is the lover of Giulio, the defense asks for mistrial and Alessandro has another trial. Who might be the killer?