Who is Colonel Haki from A Coffin for Dimitrios and what is their importance?

Colonel Haki is a mysterious figure in the Turkish police force in Istanbul. He is rumored to be head of the secret police and possibly a torturer. He is also a rakish man, flirting with women. Haki is a wannabe murder mystery writer, and he offers Charles Latimer a contrived, amateurish mystery plot to use. While Latimer is not at all interested in Haki's mystery plot, he is interested in the portrait of a real murderer that Haki presents when he tells Latimer about Dimitrios. Colonel Haki lets Latimer come with him to the morgue to see Dimitrios's body.