I absolutely love this movie and I can't see why most of the reviews I've read elsewhere are negative.
It certainly is different than your usual giallo with loads of gruesome deaths, the 'hero' who solves the case, etc.
It somehow reminds me of another Duccio Tessari's flick
[spoiler]La morte risale a ieri sera, where the father of the killed girl wants to make justice on his own[/spoiler]
As someone already said, I too started feeling, at one point that
[spoiler]Giorgio was responsible for ALL three deaths and couldn't figure out what actually happened until the very first minutes[/spoiler]
Beside the plot and the court scenes, I loved pretty much everything in this movie: the music, the locations, the choice of the actors, the direction and photography in the scene where the first victim is found in the park.
Out of curiosity, it's the skull in the locandina taken from a famous painting or something like that? I'm sure I've seen it somewhere else and only today I've realised it's NOT a skull.