If the government had left the threshhold at 0.10, would you still think the threshhold should be at 0.08? If so, why? And if not, why does that fact that the government happened to choose 0.08 as a threshhold mean that it made the best choice?
I could see sound arguments being made for 0.12 (more or less the threshhold where a person's alcohol-caused impairment starts to exceed that of other, legal, factors) or 0.15 (a point where it could generally shown, beyond a reasonable doubt, that the person's actions greatly endangered others). Even 0.10 could be justified on the premise that the alcohol might be causing a substantial degree of impairment to others, though that's getting away from the normal 'usual doubt' concept.
But the statistics show a pretty bright line in impairment around the 0.12-0.15 range (IIRC, going from 0.12 to 0.15 increases accident rates more than going from 0.00 to 0.12). If you could wave a magic wand and get all the 0.15+ drivers off the road, that would save more lives than making all the drivers below 0.10 be stone-cold sober. So why not focus resources on the 0.15+ drivers that are the biggest problem?
"If the government had left the threshhold at 0.10, would you still think the threshhold should be at 0.08? "
Yes I think the best balance is found at .08.
How about people respect that limit, leaving it where it is, and allow those very resources to be spent on other violent crime?