"It tipped," Draco answered, but he did move and sit up, stretching his arms out onto the table.
Of all people, he couldn't have Snape guess what he had been trying. Snape was as loyal to The Dark Lord as anyone. Draco had been amazed that Dumbledore had trusted him, had wanted him to tell him of his decision last year. That Dumbledore hadn't realized that would have been as good as suicide. Then again, the old man might be senile - Draco hadn't decided against that possibility.
He knew he'd have to come up with a better story, though, to get Snape off of it. Slughorn would have been far easier.