I didnt believe in Snapes innocence until i read this guys post here...
http://64.207.189.199/messageboard/index.php?showtopic=745&st=45
Reasons y Snape is not evil;
1. Severus wanted to protect Draco and/or prove his loyalty to Bella and other DE so he made an Unbreakable Vow. He may also have a soft spot for Narcissa, not romantically speaking, but as a 'friend'. After all, why would Severus be happy to sacrifice the boy and mother to the Dark Lord?!
2. The vow: when Narcissa added that if Draco failed he would be the one to do it, Severus's hand twitched. Big clue! He waited a moment, then said that he'd do it. He was thinking hard!!!
3.Why? Because he had already said to Narcissa that he had a feeling the DLord would ask him to finish the job if Draco didn't succeed. So he was already facing penalty of being discovered as a spy for not wanting to kill Albus. So why not make the UVow and take advantage of his last months as a spy with renewed confidence from his fellow Death Eaters! That's why he accepted. I think he simply thought that if he were given the occasion to kill Albus, then he would not do it and die for breaking the UVow. If not by the UVow, then by his fellow DE of course! And that is what I think was Snape's decision when he made the vow!
4. Then, I believe he informed Dumbledore which led to their argument later in the book (the one Hagrid witnessed) where they were discussing something Severus refused to do. A lot like Harry wanted to refuse Albus's orders at first about their trip to the cave, but he made Severus promise in the end like he convinced Harry later on. What promise? That if Severus had to kill Dumbledore to maintain his cover, he would need to do it and not allow himself to die as well. I believe that Dumbledore think he's less important and knew his days were numbered, he was getting weak after all, and that it would cost the war too much to lose someone like Severus. Snape knew the health status of the Headmaster, and he cured him when he came back from the Ministry in Book5. A curse which would have killed him had Severus not been there. That has only be known by very few people, maybe even only by Snape at the time. That's another big clue: why not fake it and let the man die. After all, he told Bella the only reason he never touched the Boy-who-lived was because of Dumbledore. Why not get rid of him then?! Doesn't make sense at all! But back to the promise Albus requested of Snape: he decided for Severus' sake and role in the war as the best spy ever (indeed, being the DLord's favourite has got to be good!!) that he would die if it came to that. He didn't want Snape to die in his place either for not fulfilling the UVow or blowing up his cover. And that is what he made Severus promise while Hagrid was listening!
5. When Severus came out to meet the DE, Draco, Albus and a hidden Harry, he already knew it was hopeless for Albus. It was either blowing up his cover (because the other DE didn't look ready to overstep Snape's privilege - he was the favourite of the Dark Lord, so that ought to be a good reason for allowing Snape the fatal blow!) or die from the Unbreakable Vow he made to Narcissa! In both cases, he was a goner!! But that's not what Albus wanted, and he knew Severus didn't feel inclined to do the dirty job.
6. Dumbledore knew what was coming: it was either his being killed by one of the remaining DE or Snape. Better be Snape since he was going to die anyway, so Albus couldn't gain anything from his killer. However, by killing Albus, Snape would again strengthened his reputation as a Death Eater. So why let slip that opportunity? Albus is a wise and logical man no matter how much he loves sherbet lemons!
7. So to make sure Snape did not hesitate any longer (to avoid suspicion), he pleaded Severus. Do you think Dumbledore would plead for his life?! Ha ha!! Right! No, he was pleading Severus to do it, not to mention that a man who supposedly has an ironclad faith in someone would worry for his life if he saw someone he trusted barge in to save him. When he saw Snape outside all of the sudden, he didn't 'realise' he had been duped. Nothing gave indication of that because Snape was a spy and he knew it. He knew the other Death Eaters there would refer to him as a leader. It's not like Albus had just realised that by addressing him, the other DE has blown up Snape's cover as a Dark agent. If Snape had said something like: "Poor old coot! Don't rejoice yourself, I'm not here to save you. Yes, they know me and they're my fellows. You've been fooled all this time", then yes, that would have been enough for Albus to plead Severus not to turn back to the Dark or to kill him. But there was no time for that at all! There was no time to doubt Snape's loyalty nor indication that he had remained a Voldemort follower either. No! Dumbledore immediately understood that Snape was thinking of either dying there or try an impossible rescue attempt even if there were less than a 0.01% chance of survival. There was no time to lose: Albus pleaded Severus. Not Snape, he pleaded Severus.
8. And so came the moment when they looked into each other's eyes: Legilimens surely! Eye contact makes it very potent!! Dumbledore confirmed his wish I believe. And Snape said: "All right, I'll do it for you, Albus. Farewell!"
9. And Snape did fulfill his promise: he killed Dumbledore. Remember his look of loathing: could be the same as when Harry had to give Albus the whole potion in the cave. Harry loathed himself for having to do it. Snape hated himself for having to do it and he used the hate to cast the blow that would kill Albus.
10. When Snape escaped, he did all but hurt Harry, make sure he was still giving him advice about focusing his mind and how to make it through. He also stopped someone from using Crucio on the boy on the pretext that the Dark Lord wanted him in one piece. We know the guy didn't want to kill the boy, he just wanted him to suffer. But Snape saved him. Then he escaped with Draco. He evaded all Harry's attempt. And though Snape is quite an excellent dualist, he DIDN'T do anything to the boy but give him advice.
11. One more thing before he disappeared he's beyond enraged when Harry calls him a coward. That's got to be a HUGE clue! Why would he be so insulted by that?! Because he's just given up everything he owned dear, his home and safe place by killing the man who made him into a better one! (sniff sniff). Imagine how Snape must have felt the day after!! Oh dear!! Wouldn't want to be in his shoes, not to mention he had to appear normal if he were still not alone...!
Point proven
i know i am
