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The Science of DUIs: Testing, BAC, and Concrete Evidence

The Science of DUIs: Testing, BAC, and Concrete Evidence

DUIs and DUACs may seem fairly simple, but they can be surprisingly complex. Keep reading to find out more about the science behind DUIs and what it takes to get concrete evidence in a criminal case.

About Body

The most important thing to understand about DUIs, DUACs, and criminal DUI cases is that evidence is king. If there is no evidence to prove, beyond a reasonable doubt, then accusations of a crime cannot stand. In DUI cases, evidence is almost always based on blood alcohol content which is the amount of alcohol absorbed into the blood at the time of testing.

A person’s BAC depends entirely on their unique body chemistry. Everyone has a different body composition that affects the rate and amount of alcohol that can be absorbed. Countless factors impact a body’s ability to break down alcohol.

One way to understand this concept is by looking at prescription medications. If you have been prescribed medication or an antibiotic, your doctor gives you a very specific dosage and course. The doctor prescribes medication according to body composition to account for different body chemistries that may affect the absorption of the medicine into the bloodstream. Factors like weight, age, and body fat all impact absorption.

Another way to look at this concept is by considering your friends and family. Each person has different eating habits – some may seem to always be eating but they stay lean. In general, these people have a higher metabolism meaning they can eat the same amount of food as someone else but digest it quicker. The same can be true for alcohol consumption – people with higher metabolisms may absorb alcohol more quickly than others.

This is where the idea of a “lightweight drinker” comes from. People who get ‘drunk’ quickly after only one or two drinks are often considered lightweights but the reality is they are simply absorbing the alcohol more quickly.

There are no hard and fast rules for how the human body processes substances. From food to alcohol your ability to process a drink is entirely different from someone else’s.


It’s also important to note that the kind of alcohol you drink may have a significant impact on your body’s ability to break it down and absorb the alcohol into the blood. Different types of alcohol have specific characteristics related to how it is absorbed.

For example, beer is dense alcohol that takes longer to process because it contains more micro-ingredients than other alcoholic drinks. Liquor on the other hand often has a higher alcohol content, to begin with and doesn’t take as long to absorb.

The type of alcohol you drink may also trick you into thinking you aren’t drunk. Wine is often an accompaniment to a good meal and most people drink a glass after work to relax. However, wine has a higher alcohol content than your run-of-the-mill beer or seltzer. In fact, it takes only two glasses to hit the minimum threshold for drunkenness that police measure when determining whether to charge a DUI.

Some ingredients in cocktails and mixed drinks can affect how quickly your body takes in the alcohol. Sugar makes the body absorb alcohol more quickly and can accelerate dehydration which in turn keeps the alcohol in your blood for longer periods of time.

It's important to remember that whether or not you are charged with a DUI depends on your blood alcohol content not how drunk you feel.

Charging and Testing for DUIs

When the police ask a driver to perform a field sobriety test or breathalyzer test, they are evaluating the driver’s behavior for signs of intoxication. As the body absorbs alcohol, it may affect a person’s mannerisms and balance. Many people feel weightlessness which translates to poorer posture and a lowered cognitive response time. Sometimes, a person’s eyes may track quickly back and forth, unable to focus on a fixed point. These are all signs of drunkenness.

Field sobriety and breathalyzer tests measure a person’s BAC but it’s important to note that these tests must be administered correctly to obtain an accurate result. Faulty breathalyzers or miscommunication during a field sobriety test could yield a false result that leads to the driver being charged with a DUI.

Law enforcement also uses chemical testing to verify a person’s BAC. Chemical testing occurs at the police station and involves taking a blood sample. While chemical testing is often more accurate, if the person is not tested within a certain window, their body may break down the alcohol to the point that they are no longer in violation of the law.


Your body chemistry, drink of choice, and the police officer’s ability to correctly administer a field sobriety test all determine whether you are charged with a DUI. There are countless factors at work in these cases and if one part outweighs another or there is a misstep, you could be facing DUI charges.

If you have been arrested for a DUI contact the Law Office of James R. Snell, Jr., LLC. Our team can determine whether there was an administrative error when giving the field sobriety test or if there were other factors that would prove your innocence.


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