Draco opened his mouth to speak and immediately closed it again. She could tell that he was bothered by her line of questioning, but she didn't care. He couldn't act like he was upset and sad over Ron's death when she knew that he played a hand in it. Even if it was very small, she knew that his report of Ron's potential disloyalty was likely the deciding factor in whether or not he was attacked. Maybe he'd never directly murdered someone. That didn't mean his hands were clean. Far from it, really. He simply allowed others to do the dirty work.