There is a theory that Russian dictator Josef Stalin was killed with warfarin back in 1953. He was always suspicious that someone was trying to poison him so he randomly selected someone to taste his food before he ate. The plotters figured out that they could put a few mg in his food every meal and that the random tasters would never get a therapeutic dose. Meanwhile his INR (except that they didn't use that method at the time) went higher every day. He eventually died of a brain hemorrhage. Of course his doctor had to be part of the plot because had he given Stalin a dose of vitamin K, he would have recovered. The he would probably have slaughtered a few more millions and sent hundreds of thousands more off to the Siberian prisons.