The Horror!? 59: Trauma (1978)

Fabio Testi (Italy's third important cop actor behind Maurizio Merli and Franco Nero, probably because he is always strangely mustache-less) plays Inspector DiSalvo who tries to solve the rape, mutilation and murder of a teenage girl. It doesn't take long for him to understand that she and her three best friends shared a dangerous secret, and soon the murders and murder attempts start to stack up. As if this wasn't enough, the proprietors of the exclusive boarding school that the girls attend, as well as some affluent parents aren't exactly helpful.
One of my pet theories is the absolute importance of stylization for the giallo. Nothing else is as important to decide the quality of a film in this sub-genre. Of course this does not necessarily mean that all gialli have to stylize the same things or stylize them in the same way, although many gialli tend to drift in the direction of a strangely softening stylization of violence and hysteria into something aesthetically pleasing (seen in many movies by Mario Bava or Dario Argento). Trauma chooses a somewhat different path, clearly influenced by Massimo Dallamano's What Have They Done To Solange and What Have They Done To Your Daughters and by the gritty but equally stylized hyper-realism of Italian cop movies. It takes from these sources its protagonist, its rougher (but no less accomplished) aesthetics and a deep distrust of authority figures.
And it does so very cleverly and just as self-conscious as necessary. Even the script makes an unusual degree of sense, although the final reveal is of classical giallo-weirdness.