How should I defend the narrator in the story "The Tell-Tale Heart" by Edgar Allan Poe? In my class, I am the defense attorney. I have to...

I think the best way to defend your client, the narrator of this story, is to argue he is insane. The narrator is so afraid of death that it has driven him mad. In the first line, the narrator says, "very, very dreadfully nervous I had been and am; but why will you say that I am mad?" Whoever this "you" is decided the narrator is insane, and so he cannot be found guilty because he is incapable of properly understanding both his own actions and the world around him. 

The narrator's obsession with time—at what time he does something, how long it takes to do something—is one way with which to prove this. The narrator begins the process of sneaking into the old man's room "every night, about midnight," and it takes him "an hour" to put his head through the door. He does this for seven nights, "every night, just at midnight," and feels the old man would be shocked to learn what he does "every night, just at twelve."  On the night the narrator commits the murder, "For a whole hour [the narrator] did not move a muscle" as he waits for the old man to fall back to sleep. Midnight is symbolic of death because it represents the death of day, so the narrator's obsession with killing the old man at midnight is another symptom of his maniacal fear of death and need to control it.

Further, the narrator mistakes the rapid beating of his own heart for the old man's even when the man is all the way across the room and even after the old man is dead. Before he kills the old man, the narrator says, "there came to [his] ears a low, dull, quick sound, such as a watch makes when enveloped in cotton... It was the beating of the old man's heart." This is impossible; the narrator could not possibly hear the old man's heartbeat from across the room. It is the narrator's own heart that he hears, and it speeds up and grows louder in his ears because of his adrenaline, but the narrator cannot recognize this because he is insane.  Moreover, the narrator's comparison of the sound to a watch, something that tells time, further proves his fear of death and running out of time. After the narrator murders and dismembers the old man and the police arrive to question him about a cry heard by the neighbors, his adrenaline begins to pump again. The narrator says he hears "a low, dull, quick sound—such as a watch makes when enveloped in cotton." In the final line of the story, the narrator confesses to the police that he killed the man and the sound he hears is "the beating of his hideous heart."  Again, a dead man's heart cannot beat, but the narrator's insanity makes him believe the heart he heard was the old man's and not his own. the narrator cannot healthily contemplate his own mortality, so he always imagines it to be the old man's heart he hears, the old man's time ticking away. The narrator is so obsessed with avoiding death that he kills the old man whose "vulture eye" reminds him of it (vultures are associated with death). The narrator is mad and cannot be held accountable for his actions.