The degree to which any given dose of THC affects an individual varies so wildly as to be completely useless as a baseline. To guarantee that 100% of debilitate

The degree to which any given dose of THC affects an individual varies so wildly as to be completely useless as a baseline. To guarantee that 100% of debilitated users are detected, the threshold would have to be so low as to also detect a heavy user who smoked a joint two days ago. Your argument is built on the supposition that there's a hard lower boundary on debilitating dosage. There is no such magic number, or it is nearly indistinguishable from zero.