Poe gives his unnamed narrator an air of superiority mixed with insanity. From his point of view, the narrator does not seem to find his actions entirely unquestionable. In fact, the way the story is told, the narrator is calmly explaining his thought processes of why he did what he did.
This shows us, the readers, that the mysterious narrator is, despite his best efforts and explainations, quite insane.
Poe's use of direct characterization to the readers by having the narrator implore to us to listen to his story gives the tale a sharp edge of dramatic irony.