Could I write about the narrator's obssesion in proving that he is sane rather than proving his innocence in a research paper for The Tell-Tale Heart? Is it a good topic to write about? Would I be able to write a long enough paper?
This would certainly be an easy claim to support. The narrator is obviously obsessed with proving his sanity. The narration begins as though in the middle of a conversation in which the narrator has been accused of insanity. He starts right off by telling the reader that the idea of his being insane is absurd, and then the entire story is ostensibly told to prove the point that he is not mad.
As for writing your paper, there is definitely enough to back up the idea that the narrator is more concerned with proving his sanity than his innocence. However, without being familiar with your assignment and teacher, I can't be sure that this wouldn't be seen as too obvious a claim to make. I don't think anyone would argue against you on the idea that the narrator is obsessed with proving his sanity. So how about something requiring a little more of your own opinion? Poe leaves it up to the reader to decide whether the narrator is indeed insane. What you might want to do is evaluate whether or not you, as the reader, find his claims of sanity believable. Do you believe the narrator is sane or insane? If he is sane, why does he act as he does? If he is insane, what proves that? Could a court of law find him not guilty by reason of insanity? (If this is a research paper, that would be a great topic to research!)