Apology of Common Sense

He rapes and kills, while in his spare time he writes novels. In them, he savors the smallest details of his crimes. Forensic expert Drongo has identified the maniac, but proving that he is indeed the "author" of both the novels and the crimes is not possible. Moreover, the criminal is so cunning that he has "framed" Drongo's partner, leading to the arrest of the latter. It seems that the maniac has completely outplayed the detective. And yet, the last move remains with Drongo…