I think you're being generous to the wizarding public. Lucius Malfoy can probably prove — the Hogwarts wards can possibly prove — that neither Lucius nor Draco has been in Hogwarts for quite some time. It won't be too hard for Lucius to say the better-written equivalent of "Regardless of my personal feelings for Miss Granger, I would never besmirch House Malfoy by reneging in such brutal fashion on a matter of House honor. The question at hand is this: how could Dumbledore not have known the troll was in Hogwarts? And if he did know, where was he during the attack? If you would like to propose that Dumbledore and I were in collusion on the matter — well, I'm sure a simple show of hands will make clear how likely this assembly is to believe that." Not too hard for Lucius to talk his way out of. Very much harder for Dumbledore. EDIT: I agree that not all of Hogwarts's wards are necessarily available to Dumbledore off-campus. But the mechanisms of these two wards have been described identically: Poof, he appears, and says "I felt X". I wouldn't assume by default that two wards that function identically would differ in such an important aspect. DOUBLE EDIT: It could easily be said that it makes political sense for Dumbledore to kill Hermione, as an attempt to frame Lucius. But then, if Dumbledore doesn't actually speak up against Lucius… It is complicated. But I still think Dumbledore is in trouble, just from the perspective of Eliezer taking a more serious, realistic look at events from canon.