How does Bierce's use of stream of consciousness enhance drama in "An Occurrence at Owl Creek Bridge"?

Stream of consciousness narrations are often characterized by a lack of clarity between one thought and the next, the absence of punctuation and/or capitalization, perhaps even varied and ungrammatical sentence structures.

The narration in this story does not look quite like what we might be used to in other texts that make use of this technique. However, in the third part of this story, Bierce employs a kind of stream of consciousness to show readers what it is like in Peyton Farquhar's mind as he falls from the Owl Creek bridge into the noose. This time would just consist of a second, or even a fraction of a second, and, yet, part 3 is the longest part of the narrative. Toward the end of part 1, Farquhar experienced the sensation that time was slowing down, and this perception sets the stage for part 3.

The stream of consciousness increases the drama of the story because this section is full of strange events that make us question their reality, and yet we are inclined to believe that Farquhar has, indeed, escaped execution. He experiences neck pain, certainly, but he also can perceive every minute insect crawling on the leaves in the forest, even the veins of the leaves themselves, from a significant distance.

Things feel somewhat mystical or magical—the forest is full of strange noises and voices that speak in some "unknown tongue"—and we can tell that all is not quite right in Farquhar's head, that he is confused and anxious and frightened and exhausted, and we are held in suspense, waiting to find out just what is going on.

How does Ambrose Bierce use time and stream-of-consciousness to create an unusual ending in "An Occurrence at Owl Creek Bridge"?

Bierce's short story received rave, and not-so-rave reviews for its unusual approach, which leads the reader to believe there will be a "happy ending" in a story where it will turn out the protagonist has been dead for most of it.  A Confederate planter/sympathizer is lulled into thinking he is speaking to a Confederate when a soldier in gray comes by his home one evening and they discuss the nearby troop movements, and winds up getting himself hanged for treason.  The story opens with the planter, Payton Farquhar, about to be hanged (Part 1) and the story of what led him to that point is told in flashback (Part 2).  When the narrator returns to the present, with Farquahar awaiting his fate, it appears that Farquhar frees himself and makes a heroic escape, returning home to his wife in Part 3.  Bierce articulates the details of the escape with great imagery as he drags the reader breathlessly through paragraph after suspenseful paragraph of the unlikely adventure, and for this reader at least, it seemed that  Farquhar managed to pull it off, until the final line of the story:  "Peyton Farquhar was dead; his body, with a broken neck, swung gently from side to side beneath the timbers of Owl Creek Bridge."