As I Lay Dying is written in multiple first-person narratives. Every new section is a new version of reality, particularly noticeable when the narratives overlap and cover the same event two different ways. The novel reminds us of the inherent subjectivity in any story, memory, or narrative. There are no "facts" in this novel, only opinions. Narratives toward the end of the story push the envelope even further, asking if terms like "sane" or "crazy" can ever be objectively defined, or if actions can ever be categorized clearly as one or the other.
Darl is the only trustworthy narrator in As I Lay Dying.