I'm pretty sure we're asking for trouble if we let Filch live. He probably has some nasty ability that will turn the tide for the mafia. There is a reason Snape protected him. I'm sure Snape thought about us seeing through his plans and that he would still be a target.

At least we know he's not a paranoid killer since Snape would be dead by now if he was.

I still suspect Snape so I'm fine if you guys want to go with him, I just think this is a big mistake if we don't take Filch out now. That's why I'll keep my vote.