Freeman Williams’s review published on Letterboxd :
Director Elio Petri directed several stylish features through the 60s, looking for his voice, but it wasn't until this movie, a Kafka-esque black comedy rife with political scorn that he found it, and made what is considered to be his masterpiece.
Gian Volonte is the head of Rome's Homicide Division, and on the day of his rising to the head of the Political Crime division, he visits his mistress, with whom he has a twisted, masochistic relationship: she is aroused by recreating murder scenes, and greets him with, "How are you going to kill me today?" The response is, "I'm going to slash your throat with a razor." Which he does, and then deliberately leaves plentiful clues pointing to himself as the murderer.
That is when the Kafka wheel starts turning. Every single clue he leaves is explained away by his former underlings, because they believe he surely is, as the title implies, Above Suspicion. He drops ever more extravagant clues, but still... nothing. There is one detective who begins to suspect, but even he has some doubts.
This is told alongside the Chief's grasping of the power in the Political Crime division with a fascistic fervor not unlike a dictator. Even as a bombing at police headquarters allows him to detain busloads of revolutionaries, his murder begins to pick at the former cop in him, and he finally confesses, in writing; only to find out that this still may not be the end of it.
The movie ends with a quote from Kafka (just in case you thought I was just slinging the name around). Similarly, it begins with a disclaimer, as the site used for the bomb attack was actually bombed by radicals while the movie was in post. Petri's masterpiece was more than a little prophetic, and that is scary.