are you lying to me?
The most useless question to ask someone if they are lying. Obviously, the person who is lying would not say, "Yes I am indeed!" but, in response the person would say just simply, "no". Also, if they were to say yes, then they are just plain stupid, or they gave up because they are terrible liars.
Mom: "Boy? did you hit that baseball in the neighbors window again!?"
Son: "No...."
Mom: "Hey? are you lying to me?"
Son: "O-Of course not.."
Son: "No...."
Mom: "Hey? are you lying to me?"
Son: "O-Of course not.."