A Lesson Before Dying is written from the first person narrative point of view. This means that the story is told from a character's point of view, and readers can expect the narrator to refer to himself as "I." We see this in the opening sentences of the story.
I was not there, yet I was there. No, I did not go to the trial, I did not hear the verdict, because I knew all the time what it would be. Still, I was there. I was there as much as anyone else was there.
In this story, the narrator is Grant Wiggins. First person narration gives readers a very clear view of what the narrator thinks and does, and that can be really useful; however, the first person narrative point of view is also automatically limited to what the narrator experiences, thinks, and feels. We can't know what another character is thinking or feeling unless they tell the narrator. There is one point in this book when the narrative point of view does sort of break away from first person. That occurs in chapter 29. Chapter 29 is completely composed of entries from Jefferson's diary. This means that this chapter is written from Jefferson's diary; however, readers are meant to assume that it is Grant that is reading the diary entries or is the person that has made them available to us.