While I agree the torture is definitely evil, I'd say their neutral or unaligned now. As Logan pointed out and as the DMG 3e says, alignment shifts are gradual. Except in such cases as major acts of evil/good or law/chaos, alignment doesn't shift suddenly to its opposite. A lawful good character doesn't suddenly become chaotic evil or even lawful evil without sliding through at least one or two other alignments.
Actually, having come primarily to P&P from CRPGs, I use a point system that I write down in a notebook. When a character commits an act that seems contrary to their alignment, I take note of it and add a certain number of points to the law/chaos or good/evil axes that denote a value of how much it was of a certain alignment. If they ever reach a certain number I switch their alignment to something else.
That might be overly complicated for most DMs, but it's one way of doing it. I'd also recommend being forthcoming about it with your players. Most of my players are familiar with my source material, so it's not really a problem in my case.