A judicious analyst of Italian cinema, Freddy Buache remarks: Investigation of a Citizen Above Suspicion is an attractive stylistic exercise applied to a kind of searing philosophical tale. This may, at times, turn into a pamphlet directed against the hypocrisy of the power wielded in regimes where democracy is a nothing more than an easy tag, an alibi to con-done all measures of repression.(...) The mood and psychology of the script may remind one of Simenon at his best. Yet, by dint of its inspiration, its writing, and its verve, despite a direct allusion to Kafka, it rather conjures up a caustic, Voltairean mind. In addition, the film is proof that it is still possible, within the framework of the commercial system, to make fundamentally non-conformist films, which, by dint of cynicism, humour or para-dox attain a high level of demystification". At the same time, the film gave Gian Maria Volontè, whom Petri also directed in We Still Kill the Old Way, The Working Class Goes to Heaven and Todo Modo the opportunity to display his protean talent: "By his acting alone, Volontè tells us where we are : outside reality, or this side of it. Childish, violent, obsessive, vain, "somebody", and yet despicable, both "authoritarian" and a little creep: he runs through the whole gamut. His gait, his jerks of the chin, his fits of temper portray a Napoleon laying into people, pinching the cheeks of the soldiers of the Old Guard, a Mussolini strutting laughably, groping for the words to be bawled out on a balcony. He's out of this world ".(Jean Gili)