We had a slightly homicidal CE among a mostly N/G party once upon a time. (We thought he just had a temper, not that he was completely CE!) Anyway, he waited 'til the party was occupied in a battle and then tried to take out the two people who had most recently "crossed" him. The result was pretty close to a TPK. The CE players actions were not appreciated by any of the three people who got killed that day; or the DM whos adventure setup got mangled.
I'm pointing this out because, in my situation, the disruptive player was a least playing his alignment and his goal wasnt a TPK, it was just to get back at characters who had thwarted his plans previously. But surviving in D&D is a team effort and throwing a monkey wrench like that into the works is a good way of bringing a campaign to an abrupt (and unsatisfying) end.
Anyway, if you dont want to ban this player (although s/he sounds like a source of future problems) you could have the other PCs stumble onto his/her nefarious plans. Thats going to be difficult to arrange, perhaps a Sense Motive check could tip people off that the evil PC is up to something sinister. (Allowing a Sense Motive check is almost declaring the evil PC to be an NPC, but oh well. I doubt your player is familiar enough with the rules to complain.) At least if the party knows something is up, they wont all get CGD'd in their sleep.