tools to combat drunk driving are not entirely based in science
To the point that the accuracy of breathalyzers has been challenged so many times in CA that it's to the point that if the cops in CA have you breathe into a machine and that machine returns a number that would constitute a DUI if that were your BAC then it's a DUI, regardless of what the machine actually does or whether the number in question is actually connected to your real BAC in any way.