Saying things like "I can't be sure" is just a glib narrative device to manipulate nitwits like you. It's an attempt at damage control and playing it off like he's the one who was harmed when he was the one perpetrating it. How many times in court do people who have brutally beaten someone to death say they "don't recall" or "just blacked out" or something to that effect, and still get convicted? It's an incredibly flimsy excuse, and one that no one who wasn't gullible beyond belief would ever buy.