* * Warning: I'll be talking about previous HP books * *
Okay, last month I was talking about how I think Snape really didn't want to kill Dumbledore, but did so to spare Draco from doing the deed. Since then I've reread book 6 in anticipation of the release of book 7. And I completely forgot about the Unbreakable Vow that Snape made with Draco's mother. Narcissa. One part of the vow is that Narcissa wants Snape to complete Draco's task if he can't... probably because she's worried that Voldermort would kill Draco if he failed. And we find out that Draco's task is to kill Dumbledore.
So maybe Snape had no choice but to kill Dumbledore, because he was bound to by the Unbreakable Vow? And I'm guessing that Snape told Dumbledore about it, which was why he seemed to be pleading for Snape to kill him. Both of them knew it was the only way to protect Draco.
And I don't think Snape wanted to do this. He hesitated when making that part of the Vow. He also had a look of disgust when he realized what he had to do.
So that's my theory. I've seen other theories out there as well. My SD blogging buddy, PP, takes a more hardline view with murder equalling life in Azkaban. And that's completely reasonable. I can definitely see where he's coming from. Especially since we've learned that Snape is connected to the deaths of all of Harry's parental figures.
- Told Voldemort the prophecy that led him to killing Harry's parents.
- Teased Sirius to about being stuck in the Order's headquarters while everone else was fighting, which is one of the reasons Sirius joined the fight at the Ministry.
- Killed Dumbledore with the Avada Kedavra curse.