In Harry Potter and the Deathly Hallows, when a dying Snape gives his memories to Harry, why does he trust Snape, of all people, and go to the Pensieve to see them? There are two possible scenarios (in which Snape is still on the dark side) where everything can go wrong:
It was all a ruse.
Malfoy could have told Snape about him disarming Dumbledore, and Snape could have told Voldemort about winning wands by disarming (supposing he knew about it, as an experienced wizard). So Voldemort could easily have won the wand from Snape. Supposing Snape's "death" was all Voldemort's illusion (I know magical illusions have never been mentioned, but hey) and Voldemort was lying in wait, in Dumbledore's office, for an ambush. Or Snape's memories were actually modified, and there was no need for Harry to die. In which case they were meant to lure Harry to the forest to his death. Voldemort's calling him to the forest corroborates with this.
Snape might actually have been dying, but, still loyal to Voldemort.
He could have tampered with his memories, to send Harry needlessly to his death. It sounds like the sort of thing Bellatrix Lestrange would do, but there you go. For all Harry knew, Snape was just as dedicated a Death Eater as she was.
So that's my question. If Snape was on the dark side, both of these possibilities could have resulted in Harry's death. So why did he trust him, again, of all people?