Take a look at
this if you haven't already. This is what we are playing, as said in the OP.
In all the types there are two Mafia. However, there is a Cop in only two of the four types, and both a Cop and a doctor in only 1. If Karma is really a Cop, his chance of being protected is 25% at most. Karma is smart, and would certainly not come forward on day 2. Secondly, why would he choose to investigate you, and not Downed Foes? Everyone was directing suspicion at Downed Foes, not you. Strange behaviors on Karma's part...
More importantly, there is a golden opportunity at hand. Since Karma has vouched for you, his fate is directly tied to yours. If we lynch you, and you turn out to be scum, then Karma is almost certainly scum also. Since there are only two mafia, Town would win.
But what if you turn out to be Towny? Then Karma is either a Cop, or scum. This is why I asked for a cop to give a counter claim. Lynching whoever steps up will tell us the allegiance of Karma. Or we could lynch Karma, the end result is the same either way.
But what if no one steps up? Here is where it comes to chance. If Karma is scum, you are Towny, and there is no other cop, then we are in trouble. In that case, this entire plan will fail. However, this is a chance I am willing to take. I wait a while and see if anyone else claims Cop, but if after a day or two no one has stepped up, my vote goes to you.