Ok, so it takes 2x con before a con or fortitudecheck, for an average NPC, that's 20 rounds... too long to ever make it worth the effort. That drops to half in combat, so 10 rounds. In a prison with active guards? But, a garrot does 1D6 per round, so it should take last time... of course, if the guards are level 7ish, the HP will be in the upper 40's... 8 or 9 rounds to kill. and I'm just trying to knock her out for a couple of minutes.