What Is BAC & How Is It Measured?

A short explanation on Blood Alcohol Levels.

“BAC” stands for Blood Alcohol Content, and is the percent of alcohol in your blood measured by the number of grams of alcohol per 100 millimeters of blood. BAC can be measured by small portable devices that measures blood alcohol content from a breath sample or it can be calculated by referencing a standardized “weight versus drinks” BAC chart. There are also numerous online BAC calculators that can give you a rough estimate of your BAC. Since your body’s ability to process alcohol depends on a great number of variables, including your sex, weight, number of drinks, and quantity of food consumed, there is no straightforward way to determine your exact BAC without a chemical test (from a blood sample). However, one of the easiest and most reliable ways is to use a BAC chart. To use a BAC chart you simply locate your weight and corresponding number of drinks to estimate your BAC. The only way to 100% ensure that you are not liable for DUI prosecution is to never drink and drive. If you must drink and drive, delegate a designated driver, utilize mass transit such as a taxi, bus, or train, or spend the night at the location of your party or drinking activity.

If you are pulled over for suspicion of DUI/DWI your arresting officer will likely ask you to perform a breathalyzer test and/or a field sobriety test. A breathalyzer test requires you to blow into a small portable device that will measure your BAC from a breath sample. Some types of breathalyzers are called Intoxilyzers or Alcosensors but they all perform the same test. Field sobriety tests are a series of psychophysical tests that can determine your sobriety level and your ability to drive a vehicle. The tests are standardized by the National Highway Traffic and Safety Administration (NHTSA) and can include, but are not limited to, the Horizontal Gaze Nystagmus (HGN) Test, the Walk and Turn test, the One Leg Stand, the Rhomberg stationary balance test), and the recitation of the alphabet (forwards or backwards).

If you are caught with a BAC of 0.08% or higher than you are subject to arrest and conviction for Driving Under the Influence (DUI) or Driving While Intoxicated (DWI) under California Vehicle Code 23152. It’s important to know that California has a “zero tolerance” policy for underage drinking and driving, as stated in California Vehicle Code 23136. “Zero tolerance” means that drunk drivers under the age of 21 can be arrested and convicted for DUI/DWI with even 0.01% BAC.

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Disclaimer: While every effort has been made to ensure the accuracy of this publication, it is not intended to provide legal advice as individual situations will differ and should be discussed with an expert and/or lawyer. For specific technical or legal advice on the information provided and related topics, please contact the author.

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