What factors do you think lead Krakauer to misidentify Martin Adams as "Andy Harris"?

The biggest factor in Krakauer's mistake could be found in his physical condition, which certainly hampered his ability to think clearly.

My error had greatly and unnecessarily compounded the pain of Fiona McPherson; Andy's parents, Ron and Mary Harris; his brother, David Harris; and his many friends. Andy was a large man, over six feet tall and 200 pounds, who spoke with a sharp Kiwi lilt; Martin was at least six inches shorter, weighed maybe 130 pounds, and spoke in a thick Texas drawl. How had I made such an egregious mistake? Was I really so debilitated that I had stared into the face of a near stranger and mistaken him for a friend with whom I'd spent the previous six weeks?