As this question refers to two different works of literature, I will leave it in the Literature Group.
This is a very interesting question. I think I would be tempted to approach it from discussing the reliability of the two characters. In "The Tell-Tale Heart," we are clearly presented with an unreliable narrator, who, in spite of his protestations, clearly shows himself to be on the edge of lunacy if not completely mad. You will want to consider his obsession with the old man's eye and how the sound of the old man's heart drives him into a frenzy.
With Miss Emily, on the other hand, you will want to think about how she doesn't live in the same reality as the rest of the neighbourhood. Think of how she doesn't initially accept the death of her father and then what we discover at the end about her "affair" with Barron. Certainly the boundary line between dead and alive doesn't seem to exist from her perspective - she is unreliable in the same way.
Hope this gives you some ideas to work on - certainly unreliability of the narrators seems to be key in this question.