The single easiest way to detect rotgut is just by looking at the bottle. If it's in a plastic bottle, chances are good it tastes like piss mixed with gasoline. More often than not, anyone who claims to like rotgut is a poser teenager who thinks getting drunk makes them Billy Badass.
Furthermore, a discerning drinker may consider anything below a certain standard of flavour as rotgut. If you can afford the "good" stuff, why the hell would you drink the bad stuff?
Categorized by these alert levels
Green Alert= Gastral Distress at a minimum.
Yellow Alert= Stomach pangs intensify and flatulence occurs
Red Alert= sharp pains and if have a sudden laugh you might shit yourself.
Brown Alert= shit has ruptured in your pants and you need a quick cleanup because you are disturbing others around you with the smell.
Orange Alert= gas has built up and your ass swells along with brown alert.