I imagine someone can knowingly and willfully get totally drunk. It's not that these drunk drivers can't evaluate the risks of driving because they're drunk; it's that they put themselves in the situation where such actions are even possible. Personally I find it very easy to prevent myself from drinking so much (or during some situations) such that I have absolutely no control over getting in a car and mowing down whoever's in my way.
"Words are deeds." - Wittgenstein