There is at least one other point of view from which part of the story is told. That is the point of view of the lion. Hemingway devotes an entire long paragraph to describing what the lion sees and feels, and this paragraph is a marvelous example of Hemingway's genius. The paragraph begins with:

Thirty-five yards into the grass the big lion lay flattened out along the ground.

The fact that this is indeed the lion's point of view is clear in these sentences:

All of him, pain, sickness, hatred and all of his remaining strength was tightening into an absolute concentration for a rush. He could hear the men talking and he waited, gathering all of himself into this preparation for a charge as soon as the men would come into the grass.

This is a far different style of writing than the tight, objective style of stories like "Hills Like White Elephants" and "The Killers." It shows a different, more poetic side of Hemingway and makes the intelligent reader realize that there is much more to this great writer than just a tough guy with a hard-boiled attitude.

The point of view in this story is third-person.  The narrator is a third-person one who is objective.  The narrator does not see into the minds of the characters, and only Margot knows the truth!  The narrator simply relays the events of the story and what the characters do and say to each other.  This allows the ambiguity in the story to exist. eNotes states:

It is the author's third-person narrative point of view, where the narrator does not always know what is going on in the minds of the characters he presents, that allows this ambiguity. No one but Margot Macomber can be certain of her guilt or innocence, and the narrator, who does not have access to this information, does not settle the debate.