If you do work as an expert witness on warnings, you probably feel quite confident that you know a bad warning when you see one (and would know a good one if you ever saw one). Of course, backing up our opinion with some version of, "I just know" doesn't make for very strong testimony. Indeed, we can count on our criteria being challenged by opposing council even when we can articulate them.
My first expert witness case involved a man who was injured using a chinup bar designed to fit within a door frame. The bar has rubber suction cups at each end, and its length is adjusted by twisting its two sections together or apart for a telescoping effect.