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Georgia DUI Law: Factors Influencing BAC Levels

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DUI for Excessive Alcohol Consumption in Georgia 

            First, some preliminaries – DUI arrests are often based upon the concentration of a person’s blood alcohol level. This is termed either “blood alcohol concentration” or “blood alcohol content.” It is abbreviated BAC. Skipping over some pretty important details for the purpose of brevity, the gist of this DUI category is that, in Georgia, no matter how safely you are otherwise able to drive your car, truck or motorcycle on the highways and byways of the state, if your BAC is 0.08 or more due alcohol when doing so, you are in danger of being arrested and convicted of a DUI. And, this type of DUI is often referred to as a Per Se DUI.

            Second, the formal, scientific units of measurement for BAC in Georgia is grams per 210 liters – that is, if you have 0.08 grams of alcohol floating around per every 210 liters of blood  flowing through your veins, you cannot legally drive.

            In my opinion, as a former chemistry teacher, this is a rather arcane, non-intuitive measurement scale. It’s like, instead of measuring speed in miles per hour, we decided to measure speed in miles per 210 minutes. Speed certainly can be measured thus with accuracy and precision given a properly working speedometer so crafted. But why do that? And why not just adjust the BAC scale so it’s based on 100 liters? Anyway, let me step away from that soapbox –

            Third, there are other types of DUI arrests in Georgia. For alcohol, there is the less safe DUI. This means that, in Georgia, no matter how little alcohol you have inside you – though there has to be some alcohol – if that small amount makes you even a little less safe to drive than you would be otherwise without the alcohol, you can be arrested and convicted of DUI. 

BAC and The Illusion of Time 

            If you’re like me, and you think about it for a moment, it makes sense that after having a couple of drinks, maybe it would be smart to wait an hour since having that last drink. Don’t be like me. Because I’m wrong. Turns out, BAC typically peaks for most people about one hour after consumption of their last drink. So, one hour after that last gin and tonic, that’s when you will blow your highest BAC. And don’t race home either thinking if you can just get home before the hour is up, you’re good to go. That’s so stupid only I am capable of thinking so foolishly. Right?

            Obviously, the smart thing to do is, if you’re going to have more than one drink over a couple hours, is to make other arrangements for getting to wherever you’re going next – for example, a designated driver, Uber, Lyft, etc. Once the office Christmas Party is over, after amazing everyone with your impression of how much Dave in accounting looks and sounds like an Orc from Lord of the Rings, and reminding everyone that it really is hilarious to dance around with a lampshade on your head – after all that revelry – if you have to, even sleeping under your desk is the far better, and less expensive option, compared to getting a DUI. But besides time, what else factors into BAC level? 

In the “Mood” for Some BAC Factors ?

            Some of the many other factors responsible for a person’s BAC level are not too surprising – i.e., whether or not a person ate food while they drank, the person’s weight and body type, etc. Other factors may surprise you. They did me! For instance, according to CMI, Inc., the manufacturer of the Intoxilyzer line of breath testing machines (which the police use where I practice law), even a person’s mood can affect their BAC.[1] So, here is a bullet point list of factors, ordered from “Least Intuitive” to “Well, Duh!” – at least according to this author’s preconceived notions – that may influence BAC: 

·         Mood –Stress may cause a diversion of blood from the stomach and small intestines to the muscles. This diversion may temporarily slow down the rate of alcohol absorption into the bloodstream. But, once the person becomes calm, a surge in their BAC may occur.

·         Gender – Ladies don’t have as much dehydrogenase as do men. Dehydrogenase is an enzyme which breaks down alcohol in the stomach. Female hormone levels also impact their ability to process alcohol. Also - and I’m sorry for writing this, but it’s the truth - women tend to have a higher percentage of body fat and a lower percentage of water than do men. So, all else being equal, women tend to have higher BAC levels than men drinking the same amount.

·         Weight and Body Type – Persons with lower body weight tend to be affected more by a given amount of alcohol than their heavier counterparts. Individuals with a lower percentage of body fat will have lower BAC levels than those with a higher percentage of body fat. Fatty tissue is low in water content and doesn’t absorb alcohol, so the alcohol remains in the bloodstream longer.

·         Food and Mixers – Drinking alcohol on an empty stomach results in higher BAC levels. Food slows alcohol absorption into the bloodstream by keeping the alcohol in the stomach longer. But, carbonation, i.e., mixed drinks with sodas, may increase the rate at which alcohol passes through a person’s stomach and therefore may result in a higher BAC.

·         Consumption Rate and Potency – The faster alcohol is consumed, the faster BAC will rise. Drink strength is also a variable that will affect BAC. So, as if you didn’t already know, all else being equal, pounding shots of Jägermeister over five-minutes will result in a higher BAC than sipping on a glass of Merlot over half-an-hour. See? Science is simple. 

Drunk Alcohol Level vs. Blood Alcohol Level  

            And now for a “non-factor” factor to consider in the overall picture of DUIs. Alcohol tolerance. Is alcohol tolerance really a thing? Sure is. But it does not mean that someone who tolerates alcohol “better” or has a higher tolerance has a lower BAC. It often means the opposite. Alcohol tolerance is simply a decrease in a person’s sensitivity to the effects of alcohol. What it is not is a measure of how alcohol is processed in the body. That is to say, while there may indeed be a Drunk Alcohol Level – or DAL – all the police officer, prosecutor and judge care about, at least as far as the Per Se DUI goes, is a person’s BAC.

            So, while someone who demonstrates a high tolerance to alcohol may not seem to be as intoxicated as someone without such tolerance, speaking in terms of biochemistry, their livers are eliminating alcohol at the same rate – assuming functional livers all around. That means someone who seems to be handling their drinks can have higher BAC levels than expected.

            As an aside, during my time as a prosecutor in Cobb County, I viewed the video of a man who, while standing and talking to the investigating police officer, was just as sober-appearing as Carrie Nation, albeit in drag, on Sunday morning getting ready for church.[2] This man didn’t stumble, stagger, slur his speech – nothing. But he blew over a 0.300 BAC! That’s enough alcohol to put me in a coma. There was, however, one indicator this man might be over the limit. Right there on the video, behind he and the officer, was the man’s truck with its front hood wrapped around a tree trunk. 

In Conclusion 

BAC is not a straightforward measure of one’s blood alcohol concentration. It’s not even a direct measure as it only correlates with and is proportional to the actual amount of alcohol molecules flowing through one’s blood. And, as discussed above, there are many different things that influence both BAC as an objective measurement, and impairment as a more subjective manifestation of actual intoxication. And, from a legal perspective, this article doesn’t even broach issues of BAC measurement and the accuracy and precision of the machines which the police use to get a BAC number.


[1] https://www.alcoholtest.com/bac-factors/

[2] Carrie Nation (November 25, 1846 – June 9, 1911) was a radical leader of the pre-Prohibition temperance movement. She is remembered for attacking alcohol-serving establishments with a hatchet, and described herself as "a bulldog running along at the feet of Jesus, barking at what He doesn't like." Source: Wikipedia - https://en.m.wikipedia.org/wiki/Carrie_Nation