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How Many Drinks Does it Take to Get to a .05 Legal Limit?

May 8th, 2018 DUI OWI How Many Drinks Does it Take to Get to a .05 Legal Limit?

It will take about two standard drinks to raise most people’s blood alcohol concentration to .05%.  However, there are many factors that play into a person’s bodily alcohol concentration (BAC) on at a given time and on a given occasion, and the only way to know your BAC at any given time is to submit to the police breath or blood test.

Having said that, let’s consider what .05 really means. First, a .05% legal limit ostensibly relates to the amount of alcohol in a person’s breath or blood.  Alcohol tests of a person’s breath or blood are expressed as the percentage of beverage alcohol as a function of mass. Thus, a BAC of 0.05 (0.05%) means that there are 0.05 grams of alcohol for every deciliter (100 ml) of blood or every 210 liters of breath.

Assuming the breath or blood tests used by the police actually measure bodily alcohol levels properly, in considering how many drinks must be consumed to reach a BAC of .05%, it is important to agree on the meaning of the word “drink”.  In the United States, the term “standard drink” refers to a drink containing 14 grams (0.6 ounces of pure ethanol). The following quantities typically have 14 grams of pure ethanol: 12 ounces of 5 percent alcohol-by-volume (ABV) beer, 5 ounces of 12 percent ABV wine, or 1.5 ounces of 40 percent (80 proof) ABV distilled spirits.

When counting drinks, therefore, it is important to know the ABV and the size of the pour.  Most craft beers have ABVs higher than 5 percent and are often served in quantities larger than 12 oz.  Also, popular craft drinks, such as an Old Fashioned, are often made with “over-proof” bourbon with an ABV of 50 percent or more.

Now that we know the definition of a standard drink we can turn to the scientific research which has shown that each standard drink has enough alcohol to raise a person’s BAC by approximately .02% – .025% depending on the study referenced.  Consequently, .025% times two standard drinks equal a .05% BAC.

When we consider the complexity of the human body, however, it’s clear that such simple math breaks down.  This is a question from Professor Barone’s 2018 law school exam:

  1. Three men meet for dinner, Mr. Jones, Mr. Smith and Mr. Howe.  Each weighs 160 lbs. Mr. Jones has not eaten all day and is obese.  Mr. Smith had a light lunch and works out regularly.  This is Mr. Howe’s 2nd dinner, and he works out with Mr. Smith. Each has the same amount of alcohol with dinner at 8:30 p.m.  Two hours later who will have the highest BAC?

Few of the law students got this question right, even after sitting through Professor Barone’s lecture and review on the metabolism of alcohol.  The question addresses two important variables relative to alcohol metabolism and bodily alcohol content: the type and amount of food in a person’s stomach while drinking and body mass index.  Thin people metabolize alcohol differently from thick people and drinking on an empty stomach causes a higher BAC all other things being equal.

Taken together these factors help explain why it is perilous to simply count drinks when trying to avoid a drunk driving arrest and conviction.  Thus, the only safe way to avoid a drunk driving conviction is to not drink and drive at all!  This is ironic when juries sitting on drunk driving cases will be told by the judge:

Just because a person has drunk alcohol or smells of alcohol does not prove, by itself, that the person is under the influence of alcohol. The test is whether, because of drinking alcohol the defendant’s mental or physical condition was significantly affected and the defendant was no longer able to operate a vehicle in a normal manner.

In other words, it’s not unlawful to drink and drive in Michigan, and a jury can’t convict on this basis alone.  Unfortunately, this means you are being set up to fail because you can lawfully drink and drive, but if you do, there’s no way to know you won’t be convicted of drunk driving until you take the police test.  Making matters worse, you are not “safe” simply because you have a BAC less than .05 or even .08.  The reason this is true because in Michigan drunk driving can be proved when a prosecutor can show, beyond a reasonable doubt, that a person’s ability to operate a motor vehicle is materially and substantially lessened due to the consumption of alcohol.  This definition of drunk driving in Michigan does not even contain a legal limit.

From this explanation, two things are evident; first, there is no need to reduce the legal limit in Michigan because .05% BAC is already illegal provided the prosecutor can show that the alcohol significantly impacted the person’s ability to drive their car.  Second, lowering the legal limit will cause more people who can still drive perfectly to be convicted of a serious and potentially life-changing crime.