Firstly, I’m pretty sure Quirrell did it, because (a) he did it in canon and (b) we know he’s voldemort and he’s trying to turn Harry dark (c) he tried to persuade Hermione to leave. But Dumbledore knows none of this, with the possible exception of (c).
First, if it were Lord Malfoy, the assassination would doubtless be for honor, which means that it should be recognizably the work of the Malfoy family. That means death via snakebite. Such an obvious killing may affect Harry’s debt, or create a new blood debt in Harry’s favor, but as has already been demonstrated Lucius doesn’t care about that very much. A mountain troll… doesn’t really have very much to do with Lucius Malfoy. It doesn’t fit the pattern.
Lord Malfoy does not hold absolute power, and even if he could avoid punishment for murder, it would cost him political capital, he would lose swing votes and so forth. But he is not stupid, and so might kill in an uncharacteristic way because it is uncharacteristic. Yes he would want some people to recognize his revenge, but some of the wiser wizards would realize it was him anyway, and he could privately confess it to intimidate his enemies while publicly denying it to minimize the fallout.
Second, the Marauder’s Map Confunding doesn’t make very much sense. Lucius could do a lot with an Imperiused professor, but indiscriminate Legilimency doesn’t seem like one of those things.
I think Fred and George are old enough to leave hogwarts and visit the nearby village, in which case they could have been ambushed there. Do we actually know whether Imperitused people can perform memory charms? He could also have got one of his allies to do this, either a teacher or one of the older students, although this would be more risky.
Fourth, and finally, Lucius would have to somehow find a way to circumvent the Hogwarts wards.
I’m not sure how the wards work, nor who has permission to alter them. There is at least one charm that affects only dementors, so its possible that the wards might be able to detect dementors but not trolls, but that’s just conjecture.
Finally, if there is no way this could have been organized by anyone but a Hogwarts professor, then the finger of blame points squarely at Quirrell, and I think Quirrell is smart enough to avoid that (e.g. if magical creatures cannot be sneaked past the wards, why not smuggle in a lion and cast spells on it to stop magic affecting it?).
Therefore, when Dumbledore looks at the evidence there is going to be sufficient doubt over who did it, and also the secrets of Salazar Slytherin will not be implicated. If Quirrell can devise a plan to break Belltrix out of prison, he can murder a girl without getting caught.
Not to say that Harry won’t realize it was him eventually, but only after more evidence, a lot of deduction and only a few chapters from the stories’ end :)
Firstly, I’m pretty sure Quirrell did it, because (a) he did it in canon and (b) we know he’s voldemort and he’s trying to turn Harry dark (c) he tried to persuade Hermione to leave. But Dumbledore knows none of this, with the possible exception of (c).
Lord Malfoy does not hold absolute power, and even if he could avoid punishment for murder, it would cost him political capital, he would lose swing votes and so forth. But he is not stupid, and so might kill in an uncharacteristic way because it is uncharacteristic. Yes he would want some people to recognize his revenge, but some of the wiser wizards would realize it was him anyway, and he could privately confess it to intimidate his enemies while publicly denying it to minimize the fallout.
I think Fred and George are old enough to leave hogwarts and visit the nearby village, in which case they could have been ambushed there. Do we actually know whether Imperitused people can perform memory charms? He could also have got one of his allies to do this, either a teacher or one of the older students, although this would be more risky.
I’m not sure how the wards work, nor who has permission to alter them. There is at least one charm that affects only dementors, so its possible that the wards might be able to detect dementors but not trolls, but that’s just conjecture.
Finally, if there is no way this could have been organized by anyone but a Hogwarts professor, then the finger of blame points squarely at Quirrell, and I think Quirrell is smart enough to avoid that (e.g. if magical creatures cannot be sneaked past the wards, why not smuggle in a lion and cast spells on it to stop magic affecting it?).
Therefore, when Dumbledore looks at the evidence there is going to be sufficient doubt over who did it, and also the secrets of Salazar Slytherin will not be implicated. If Quirrell can devise a plan to break Belltrix out of prison, he can murder a girl without getting caught.
Not to say that Harry won’t realize it was him eventually, but only after more evidence, a lot of deduction and only a few chapters from the stories’ end :)