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Breath Test Results During The Absorption Phase: Not Reliable 

Posted by Richard Wagner | Feb 29, 2024

Alcohol's Path Through the Human Body

The alcohol you drink enters your stomach, and then your small intestine, where it circulates through your blood. After absorption, the alcohol is distributed to the organs and tissues. It then affects your brain and central nervous system. Your ability to drive is not affected by the alcohol your body has not yet absorbed.


Photo by Jack Van Hel on Unsplash

Because alcohol is absorbed, distributed, metabolized, and eliminated over time, the police officer asks you questions:

  • what you were drinking
  • how much
  • when you started and stopped drinking
  • where you were drinking
  • when was your last meal, and
  • what you had to eat

These questions relate to the different factors that affect the absorption of alcohol discussed below. Unfortunately, the police do not tell you that you do not have to answer these questions. 

The Alcohol Curve

This alcohol curve is used to show how your blood alcohol concentration (BAC) (increases) rises toward a peak (maximum BAC), and then falls or decreases. 

The amount of alcohol in your body is measured by the weight of the alcohol in a certain volume of blood. This is called the blood alcohol concentration (BAC). BAC is expressed as either 0.08 grams of alcohol per 100 milliliters of blood or 0.08 grams of alcohol per 210 liters of breath. VC 23152b.

Absorption Phase

The left side of the alcohol curve is the absorption phase. This shows your BAC going up over time.

During the absorption phase, the alcohol concentration in the arteries is much higher than in the veins.

According to one of the leading scholars on the subject, Dr. Kurt Dubowski, the difference between arterial blood and venous blood can range between 50-100%. Absorption, Distribution, and Elimination of Alcohol: Highway Safety Aspects, Journal of Studies on Alcohol, Supp. 16, July 1985, p. 99.

The lungs have a higher alcohol concentration than the brain. The brain is the location where alcohol affects your ability to drive safely.

Because alcohol that has not been absorbed cannot cause driving impairment, there is a huge debate over how long this phase lasts.

The prosecution typically argues that absorption is complete almost immediately after you finish your last drink. However, according to to Dr. Kurt Dubowski,

it is often impossible to determine whether the postabsorptive state has been reached at any given time,” Absorption, Distribution, and Elimination of Alcohol: Highway Safety Aspects, Journal of Studies on Alcohol, Supp. 16, July 1985, p. 105.

There are many factors that affect how quickly alcohol is absorbed into the blood, such as the type and amount of food in the stomach, whether the person has any GI diseases, and whether they have taken any other drugs (such as aspirin). These facts are often ignored by the  prosecution. When any of the factors are present, absorption can be delayed by 2 to 6 hours. See, Goldfrank's Toxicologic Emergencies, Ninth Ed., Lewis M. Nelson, MD, et al.

Other factors that affect absorption:

  • gender
  • body composition/age
  • ethnicity
  • drinking pattern
  • type of drink
  • strength of drink
  • mental state 

Elimination Phase

The right-hand side of the curve is also known as the post absorptive or elimination phase. The elimination phase shows how your BAC decreases as time goes by. After you reach your peak or maximum BAC, your body begins to flush the alcohol from your system.

Elimination rates generally differ from person to person but are typically between .015 and .020 percent per hour. This is in contrast to unpredictable absorption rates, which vary widely.

However, AW Jones, a renowned academic scholar in this field of study, warns in a peer-reviewed article that attempting to “measure the elimination rate from two randomly timed tests is seriously flawed.” Physiological variations in blood ethanol measurements during the post-absorptive state, Journal of the Forensic Science Society, 1990; 30: p. 280.

Just like there are many factors that affect absorption, many things affect the rate of elimination, such as: how much you drank, your drinking pattern, and whether you had anything to eat while you were drinking.

DataMaster DMT Breath Testing Machine


As your body absorbs the alcohol into your bloodstream, the alcohol is unevenly distributed throughout your body – it is not in equilibrium. If you are given a breath test while you are absorbing, the test result will likely be a high reading that is not an accurate measurement of your BAC.

Imagine dumping a jug of chlorine into one end of the swimming pool. Without waiting for the chlorine to circulate evenly throughout the water, you took a sample of the water to measure for chlorine. If you took a sample of the water at the end of the pool where you just poured it, you would get a falsely high reading.

Keep in mind, this happens even if the breathalyzer is perfectly calibrated. The breathalyzer is unable to tell the difference. One of the leading experts in the field has documented the problem that occurs when drivers are breath tested during the absorption phase:

“… results from data in the literature indicate that breath testing is not a reliable means of estimating a subject's BAC during absorption. The results also indicate that there is a significant likelihood that a given subject will be in the absorptive state when tested under field conditions. …breath test results consistently overestimate the result that would be obtained from a blood test by as much as 100% or more. G. Simpson, Accuracy and Precision of Breath Alcohol Measurements for Subjects in the Absorptive State, CLINICAL CHEMISTRY, Vol.33, No.6, 1987, p. 756.

There may be other flaws in the evidence in your DUI case, this is just one of them. If you have been arrested for a DUI and took a breath test, contact The Law Office of Richard Wagner at 714.721.4423.

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Richard Wagner

Attorney Profile Defense Lawyer Richard Wagner upholds and defends freedoms and liberties enshrined in our United States and California Constitutions.  “Richard was able to achieve an even better outcome for my case than what we initially thought was possible. I couldn't be more grateful to h...