Massachusetts DWI DUI OUI Field Sobriety Test Police Training Manual

spends drinking, on whether the person is a man or a woman, on how large the person is, on whether the drinking takes place on an empty stomach, and on certain other factors. But let’s take as an example a 175-pound man. If he drinks two beers, or two shots of whiskey, in quick succession on an empty stomach, his BAC will climb to slightly above 0.04. Two more beers will boost him above 0.08. One more will push him over 0.10. In one respect, then, it doesn’t take very much alcohol to impair someone: “a couple of beers” can do it.

But in another respect, when we contrast alcohol with virtually any other drug, we find that impairment by alcohol requires a vastly larger dose than does impairment by the others. Consider exactly what a BAC of 0.10 means. Blood alcohol concentration is expressed in terms of the “number of grams of alcohol in every 100 milliliters of blood.” When we find that a person has a BAC of 0.10, that means that there is one-tenth (0.10) of a gram of alcohol in any given 100 milliliter sample of blood. One-tenth of a gram is equal to one hundred milligrams (a milligram is one-thousandth of a gram). So, at a BAC of 0.10, the person has 100 milligrams of alcohol in every 100 milliliters of blood, or exactly one milligram per milliliter.

Note: The term BAC is used in the manual. However, it should be understood to refer to either Blood Alcohol Concentration (BAC) or Breath Alcohol Concentration (BrAC) depending on the legal requirements of the jurisdiction.

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