I've actually covered that scenario. Here's a quote I made earlier:
"The issue, and why I didn't want to bring this up earlier, is if scum or the real SK realize this would happen. Then they simply withhold a kill to frame her. However I kind of just realized that that doesn't really matter. BSP is (in my mind) neutral right now. And can't vote. Losing her due to her being framed tomorrow doesn't hurt town. In fact, that means scum/SK traded a kill in order to get a neutral player lynched, and a player who was prime lynch material already. Seems like a shit trade. "
Also if they do actually decide to make that trade, the solution is simple. If we find 1 kill only tomorrow, and then vote off BSP, and then she turns out to not be the SK, we need to look HARD at anyone who voted for BSP today. That includes me to be honest. The real serial killer would almost certainly be pushing for BSP's lynch today. Or they are letting me and nin do the work.