So the reader can see the point of view that the writer is in.
The story in question is The Guilty Party which, at the very end, switches point of view.
The point of view we see from then is perhaps the soul of someone who died and who is waiting, watching as they bring Liz's soul.
The reason for this is to paint the confusion, dream-like state and to underline the point of Liz dying, as well as to explain closely how is the case looked 'on the other side'.
Switching to the first person, the author tried to convey a sense of the other side better to the reader; the confusion, dream-like state, weirdness of it. This way we can see even closely the guild her father had over her upbringing if it has transferred to the other side and the world of the deceased, as well as Liz's vindication from the close point of view of someone who is personally witnessing it.
The sudden shift in the point of view is to make the reader experience the intensity of the situation which the narrator is trying to explain. Just for the sake of experience.
The Point of view is an aspect of story writing where the reader might experience the narration in different point of view. There are three perspectives, first person, second person and third person perspective.