Many would argue that this film is not a giallo in the strictest sense, and I would agree. However, the frank manner in which it deals with the topics of violence and sexuality, as well as the style of the end reveal, position it as a close cousin of the genre.
As usual with a Fernando di Leo film the story packs a punch, and is full of caustic social commentary. This is one of his earliest films, and his casual-yet-leery attitude towards the baser human instincts (read: sex and violence) is already apparent. Before any of you sex-obsessed gorehounds rush out to buy a copy of the film, I should point out that 99% of the sex and violence is of an oral nature (that's 'oral' in a spoken word sense you perverts).
Also as is typical with a di Leo film, there is little-to-no directorial style on display. He can't seem to resist letting a cameraman walk shakily around half-naked women, often getting them (cameramen) to shoot from a high or low angle in an attempt to infuse proceedings with a modicum of panache. That approach actually works reasonably well here, as it provides a pivotal rape scene (seen both in the opening credits and towards the close of the film) with a rough-and-ready edge that makes it all the more shocking (before anyone suggests that this is evidence of a skilled director, watch the love scenes in Avere Vent'anni, which are supposed to be light-hearted, and are shot in exactly the same way).
The central thrust of the film, as Pier Paolo Capponi investigates a group of delinquents who rape and murder their teacher, bears comparison to many a giallo. Unfortunately, as with the sex and violence, most of the investigation involves people sitting around and talking, which renders the first half of the film in particular ponderous and slow. The film's attitude to sexuality, shortly to become one of Argento's favourite themes, seems initially progressive, with a couple of mostly-gay characters. This is undone slightly by the revelation of the motive of the killer, which can be boiled down to the fact that they are mostly-gay.
For further evidence of di Leo's shaky credentials as a director (and the shaky hands of his cameramen), look no further than his handling of the killer's reveal. I wasn't even sure who the killer was on first viewing, as the shot which reveals their identity is a classic di Leo handheld one (shaky), and the killer's face is clearly shown for only a second or so. (Despite not actually carrying out the murder, the character in question functions as a de facto 'killer', as this is one of those films where those guilty of the murder are evident immediately, but the thrust of the investigation is to discover who is the mastermind behind these actions).
The identity of the 'killer' is also extremely unsatisfactory. Most gialli (and, indeed, murder-mysteries in general) have some sort of narrative progression, where the investigation throws up various leads and red herrings. Whether or not these leads actually lead, so to speak, to the killer is almost beside the point (most of Argento's best gialli contain investigations which ultimately have little to do with the eventual unmasking of the killer); the important thing is that they provide cinematic entertainment. The one lead in Naked Violence, a single word uttered by one of the accused boys, gives rise to a single ten minute investigative sequence in which Capponi and Susan Scott (who is given next-to-nothing to do in this film beyond making one speech about how the accused are human beings) speak to a few people who knew the boys, or may have information relating to them. As the film draws to a close, it becomes sadly apparent that the guilty party must be one of the people encountered by Capponi and Scott in this sequence, which means they have appeared on screen exactly once prior to the Big Reveal.
As I've probably made clear, this film is a failure as a giallo. However, di Leo didn't make it as a giallo. What he could do, and was extremely talented at, is sculpt crime films which pack more of a punch, and seem more rooted in reality, than any other Italian genre director of the time. While he would scale far greater heights than this in future films (particularly The Boss and Milan Calibro 9), if you want to see a film wherein he took the first tentative steps towards those masterpieces, and if you have a passing interest in the dubious recreational habits of Italian working class teens in the late 60s, you might get something out of this. If you're a sex-obsessed gorehound, get di Leo's later giallo, Asylum Erotica.