As Balko notes, there are several causes of driver impairment other than alcohol. A 2001 American Automobile Association study found that eating, adjusting radios or GPS devices, and having kids in the backseat could impair a driver as much as or more than having a BAC of 0.08. And although texting while driving is a traffic violation in many states, talking on a cellphone while driving is not. Regardless, a texting-while-driving ticket costs less and does far less damage to a person’s reputation than a DUI conviction or even arrest. The difference between these causes of impairment is that an amount of alcohol or drugs can be accounted for in a person’s blood or breath while proving that a person had been driving recklessly because they were distracted by their kids is not quantifiable. Again, though, as Acevedo explains, neither is alcohol or drug impairment.
Of course, if you can measure the amount of alcohol or drugs in a person’s blood and you can’t measure impairment due to other distractions, why not just take what you can get and prosecute impairment you can prove? Most people would agree that the answer is obvious – it’s unfair. But this is how the majority of DUI statutes function in the United States. And while, as Balko says, it may all be about “a lingering hostility toward demon rum,” there is also the question of the spirit of the law. DUI statutes are about keeping the roadways safe. When they serve this aim – as well as raise huge amounts of revenue and unduly punish citizens who casually drink alcohol – they undermine their true purpose.