Describe two traits of the narrator of "The Tell-Tale Heart" that ultimately lead to his downfall.

Because of the way in which the murderer is presented as
an unreliable narrator, lots of uncertainty exists about his character and the astute
reader must infer lots of the information we can glean about him. However, if we look at
the ending, we can suggest the two following traits that are responsible for the
narrator's downfall.

Firstly, it is clear that the narrator
takes pride in the way he has committed what appears to him to be the "perfect" murder.
He says that there was no blood at all, because he "had been to wary for that. A tub had
caught all--ha! ha!" His arrogance and the way he gloats at his intelligence leads him
to talk to the men and position himself right above the
body:

I
brought chairs into the room, and desired them here to rest from
their fatigues, while I myself, in the wild audacity of my perfect triumph, placed my
own seat upon the very spot beneath which reposed the corpse of the
victim.

It is clear that this
belief in his own "perfect triumph" and the narrator's arrogance is thus one key trait
that leads to his discovery and capture.

Secondly, although
this is not made clear, I believe that the sound of the beating of the old man's heart
actually symbolises the internal guilt of the narrator in committing the crime that he
is apparently so unaffected by. It is obvious that the sound of this beating is heard by
the narrator alone, and what is interesting to spot is the way that this sound has the
effect of driving the narrator into a kind of lunacy:

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I foamed--I raved--I swore! I swung the chair
upon which I had been sitting, and grated it upon the boards, but the noise arose over
all and continually increased. It grew
louder--louder--louder!

Perhaps
we can read this as being the conscience of the narrator demanding to be heard. Thus we
could say that it is the guilt of the narrator that secondly is responsible for his
downfall.