Okay.

Hermione knocks on the door of the Headmaster's office, while Harry and Dumbledore are having a chat. "I thought you'd like to know," she says, "I'm going to kill Draco Malfoy." She then turns around and leaves. Harry laughs nervously, but Dumbledore looks worried. "We probably ought to follow her."

They arrive at the trophy room just in time to see Hermione stun Malfoy and cast the blood-cooling charm on him. She turns around and sees Harry, and smiles. "Well, now you're safe, Harry."

The subsequent investigation reveals that, as a protest against Binn's teaching, she'd been submitting plans of ways to kill Malfoy as her homework for months now, and then stopped a week ago, with the last one involving the blood-cooling charm.

What's Harry's probability that Hermione was the hand behind the dagger? (Or, to put it another way, is there enough evidence out there that's stronger evidence for "Hermione did it of her own free will" than "Hermione was the pawn in someone else's game" that could put Harry up to even 5% probaiblity that Hermione did it herself?)