The Bloodstained Butterfly (Una farfalla con le al (1971)

When a young female student is savagely killed in a park during a thunderstorm, the culprit seems obvious: TV sports personality Alessandro Marchi, seen fleeing the scene of the crime by numerous eyewitnesses. The evidence against him is damning... but is it all too convenient? And when the killer strikes again while Marchi is in custody, it quickly becomes apparent that there's more to the case than meets the eye...