How could you prove that Miss Emily is guilty of premeditated murder and is not insane?

In "A Rose for Emily," Emily cannot be convicted of either
one, really.  She's dead.  That's the whole point of the story.  The town is clueless.
 It's the worst piece of detective fiction in the history of
literature.

Obviously, she might have been convicted of any
number of crimes if the townspeople would not have institutionalized her (treated her as
such a monument and pillar of the community).  They can't even get her to pay her taxes.
 How are they going to have the guts to charge her with murder or, worse, insanity?  She
doesn't even need a lawyer.  The town is too scared to even enter the house, let alone
deliver a subpoena.

The signs of premeditation are there:
she buys rat poisoning, Arsenic.  The town, though, mistakenly thinks she's going to
kill herself because no one will marry her.  What?!  They honestly thought and even
condoned suicide over being an old maid.  What fools!

And
there's evidence: a certain fat decomposing body in the bedroom.
 Hello?

After she buys the arsenic, she is seen with Homer
Baron the very next day.  Even though he is a Yankee and openly gay, they also condone
the marriage.  Fools again!  They don't see signs of murder or poisoning even after he
disappears and the smell of a dead body fills the
neighborhood.

Putting Emily on trail for pre-meditated
murder is like putting Oedipus on trial for being blind: it's rather obvious.  CSI is
not needed here.