Why does Faulkner use a series of flashbacks to narrate the events in "A Rose for Emily"?

Don't forget that "A Rose for Emily" is considered both a
Gothic short story and a murder mystery.  The events in the
narrative are not told chronologically, but rather, by a series of flashbacks which
resemble vignettes.  Vignettes are short impressionistic scenes,
which purposefully paint a character, scene, or idea in a very particular
light.

This technique in "A Rose for Emily" accomplishes a
few things.  First, it builds up the mystery and suspense surrounding Miss Emily, and
makes the surprise ending all the more shocking and gruesome.  Also, it serves to
characterize Emily, her father, Homer Baron, and the rest of the small town against each
other.  The reader is not given enough information and does not have a broad enough
perspective to make a well educated assessment of characters and events.  Rather, it is
only possible to compare characters and events to everyone else and everything else that
happens in the story.  This heightens the Gothic elements of the novel; the narrator's
bias emphasizes that perhaps the Griersons are not the only thing in this town that is
slightly eerie and not to be trusted.