Walckner Law Office

​Attorney James Walckner​​

A driver’s blood alcohol concentration (BAC) can be reliably measured using a breath or blood sample.  Presenting a winning defense requires a comprehensive understanding of the science behind these readings.

Alcohol in the Body

Alcohol is absorbed into the body’s blood stream when a person drinks alcoholic beverages.  The rate alcohol is absorbed is affected by the health of the person, the amount and type of stomach contents, and the amount of alcohol in a drink.  This process of ingesting alcohol and it traveling to the bloodstream is referred to as the Absorption phase.

Alcohol is water soluble, meaning it is drawn to water.  Once in the blood stream, alcohol is distributed in proportion to the water content of the body’s tissues.  This is known as the Distribution phase.  This is the reason alcohol tends to affect smaller people more than larger people, and women more than men.  Here’s why: A person weighing twice as much as another has twice as much water in the body.  The same amount of alcohol is dispersed more in the heavier person, causing it to have less affect.  The same science explains the affect of alcohol on men versus women.  Men have 68 lbs. of water for every 100 lbs. of body weight.  Women have 55 lbs. of water per 100 lbs. of body weight.  This means alcohol is dispersed more in men, reducing the concentration and giving it less effect.

The body eliminates most alcohol through the liver.  A person’s blood alcohol concentration begins to decrease when the absorption rate falls below the elimination rate.  Drinking coffee, exercising, or eating food does not cause the liver to work faster or accelerate the elimination process.

Retrograde extrapolation is the process of predicting what an alcohol concentration was earlier based on a BAC reading obtained later.  This becomes especially important in cases where there was a delay of more than three hours in obtaining the breath or blood sample.  A significant amount of information is necessary to calculate a person’s BAC at the time of offense using this method.  Put simply, a toxicologist utilizes a formula that adds the amount of alcohol eliminated from the body to the BAC reading.  An OUI defense attorney can complicate a prosecutor’s case by arguing a driver had not been far enough along in the body’s processing of alcohol to cause impairment at the time of offense when there is a delayed BAC reading.  In simpler terms, a person is not impaired immediately after ingesting alcohol; the body must begin the distribution phase to become affected, and that takes time.

How Breath Test Instruments Work

The liver eliminates most alcohol from the body.  The remainder is eliminated through sweat, bodily fluids, and exhalation.  The breath contains evidence of alcohol ingestion in people who consumed alcohol.  There is a relationship between the amount of alcohol in a person’s blood and the amount of alcohol contained in expired air.  The ratio of alcohol in a person’s breath to alcohol in the blood is approximately 1:2100.  Breath test instruments use infrared light that is absorbed by alcohol molecules in the breath.  The relationship between the amount of light that passes through the breath sample and the amount of light absorbed by alcohol molecules allows for a calculation of a person’s BAC.

​Measuring Blood Alcohol Concentration