As explained, the unknown narrator is unreliable due to his lack of mental stability. The exactness with which the narrator recounts murdering the old man, as if his stealthy way of executing the crime is evidence of his sanity, reveals his monomania and paranoia. He attempts to prove his sanity by murdering an old man in his sleep due to his blind eye, but resists and explains his thoughts to the reader as “but I found the eye always closed; and so it was impossible to do the work; for it was not the old man who vexed me, but his Evil Eye.” (Edgar Allen Poe 1). This further proves that his mental state is crumbling for he sees the old man and the “Evil Eye” as two different beings. However, he ends up killing the old man to rid himself of the eye as well, giving more evidence he is unreliable and insane.
Further evidence that the unnamed narrator lacks sanity is that after committing the crime of homicide and the police arrive, he is convinced that the now dead old man’s heart is still beating. His guilt takes on the form of a hallucination to the point where he is convinced even the policemen can hear it and suspect him as a murderer. In the end, his guilt drives him to cry out and tell the police to tear up the floorboards to reveal the corpse of the old man he murdered and then dismembered. The story is driven not by his insistence upon his innocence but by insistence on his sanity and to prove that only a sane man