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Posted: 30 December 2014
Updated: 16 December 2017

Discussing blood alcohol levels in English

Stack Exchange

Question from English Language & Usage on Stack Exchange

Which units/terms are usually used to discuss blood alcohol levels in English? Wikipedia suggests that people use percent in the US and basis points in Great Britain. On websites devoted to the topic, I found the expression BAC (blood alcohol content) followed either by a percentage or a number. In my native language German, the unit permille is typically used, but I don’t recall seeing permille used in English in this context.

How do native speakers express the fact that a person had a certain BAC, that is, how would they complete sentences such as

According to the police report, his blood alcohol content was …

or

The legal limit for driving a car is …

(Strictly speaking, there are several ways of expressing a certain BAC because there are several different units. However, I am most interested in the expressions used in everyday English, rather than those used in legal or scientific documents.)

My answer

[Read, comment, and vote on my answer at Stack Exchange]

I prosecuted people for DUI in the state of Illinois, so I may be able to offer a perspective of the legal jargon, the police vernacular, and the language of the lay person. To me, the following road sign speaks volumes:

08bac-road-signThe sign is an official government sign to warn the population. It does not mention units at all. David Garner is right that extremely few people in the US could name the unit involved. I know from working with police officers and from attending training for prosecutors who prosecute DUIs that most police officers and lawyers cannot describe the unit of measurement.

As further evidence of the lack of understanding of the unit of measurement, some people will make statements such as, “Susan had a point oh six and Jack had a point twelve, so he was twice as drunk as she was.” Of course, BAC is not a magically precise measure of the degree of impairment, but because most people do not understand what is being measured, they cannot make proper comparisons between different BAC values.

To explicitly address your two examples, in my opinion, a non-professional writer but native speaker of American English would write the following:

According to the police report, his blood alcohol content was .16.
The legal limit for driving a car is .08.

I believe they would say “.16” as “point one six” and “.08” as “point oh eight.”