Actions which unreasonably endanger other people are mala in se (bad in and of themselves); actions that don't endanger or harm other people are mala prohibitum (bad merely in that they are prohibited).
If it can be proven beyond a reasonable doubt that someone committed an act that was mala in se, then it is just and proper that such a person should be punished.
Driving on public rights of way with a BAC of 0.15 unreasonably endangers other people; I don't think there is anyone who can drive safely at that level of intoxication. Thus, if someone is found to have been driving with such a BAC, that pretty well proves beyond a reasonable doubt that they were unreasonably endangering other people. On the other hand, even if some people would not capable capable of driving effectively at a 0.08, others would. Thus, a BAC of 0.08 in and of itself does not constitute proof beyond a reasonable doubt that the person's actions posed an unreasonable risk to others.
If someone blows a 0.07 three hours after a crash, that would tend to provide substantial evidence that their BAC was much higher at the time of the crash, and (absent some substantial rebuttal evidence) tend to prove beyond a reasonable doubt that their actions endangered others. But if someone boards his car with a 0.080 and does not show any outward signs of difficulty driving, the 0.080 would not prove beyond a reasonable doubt that the person's actions unreasonably endangered anyone.
"Driving on public rights of way with a BAC of 0.15 unreasonably endangers other people; "
SO does .08 as function is shown to be deminished at that level. This makes it a will danger imposed upon others that drive on the same roads.
It is entirely unreasonable to willfully endanger another person. I do not see how that statement can be doubted.
"Thus, a BAC of 0.08 in and of itself does not constitute proof beyond a reasonable doubt that the person's actions posed an unreasonable risk to others."
Being that it is a willful act, and it is known that almost all people show signs of decreased capability, I would argue that the risk in unreasonable beyond doubt.
"If someone blows a 0.07 three hours after a crash, that would tend to provide substantial evidence that their BAC was much higher at the time of the crash"
If the guy that hit me blew a .07 when tested he would not have been charged with DUI. (had he been 21 that is)
My brother was stopped and he blew something just over a .07 and he was released without charge. Yes he was arrested, yes he was detained, that has been found to be a proper action by law enforcement to take.
Denying the people that are harmed or killed by drivers between .08 and .10 is what I would offer as unreasonable.
That number is not insignificant being that one number I found was over 3 thousand people in a year.