Last Updated on July 2, 2025
BAC is an abbreviation for Blood Alcohol concentration, which estimates how intoxicated someone is while driving. Under California law, the maximum BAC someone can have while driving is typically 0.08%, but commercial drivers must have a BAC below 0.04%, and minors must not have a BAC above 0.01%. If your BAC is above the legal limit, you will usually be charged with driving under the influence of alcohol. However, if the officer believes you are driving while intoxicated, you can still face DUI charges.
What Does BAC Stand For?
BAC is an acronym for Blood Alcohol Concentration. Sometimes people use BAL or (Blood Alcohol Level) for the same purposes. Blood Alcohol Concentration is a means of measuring how much alcohol a person has in their system. A person’s BAC can be measured through blood, breath or urine tests, though in California, only blood and breath tests are used to estimate how much alcohol a person has consumed prior to driving.
How is BAC Measured?
A breathalyzer technically does not estimate how much alcohol is in a person’s blood, but actually how much alcohol is in their breath. This distinction is important as it is a cornerstone of many common DUI defenses.
Additionally, neither blood nor breath tests calculate the BAC at the time of driving, which is what matters under the law. This fact can be used as a defense under the rising alcohol theory. Lawyers can also challenge the result of the blood test or breathalyzer if they believe either was administered improperly.
What Does BAC Measure?
A BAC measurement does not take into account how intoxicated someone is. All people react to alcohol intoxication differently, so it is extremely subjective to ask police officers to evaluate if someone is or is not too drunk to drive based solely on their behavior. Indeed, two people with the same BAC measurement can act entirely differently; one may still seem sober while the other falls down drunk. Scientists from the National Highway Traffic Administration have shown that while two people may act very differently with the same BAC, almost everyone will drive less safely once they have a Blood Alcohol Concentration of 0.08%
Because people can act so differently depending on how much they drank, California state law allows officers to arrest people for DUI even when their BAC is below 0.08% as long as the officer believes them to be intoxicated. In these cases, it is common for DUI defense lawyers to get the charges reduced to wet reckless since there is insufficient evidence to show the defendant was Driving Under the Influence.
BAC Doesn’t Matter in Cases Involving Drugs
Many people wonder what the legal BAC is for intoxication with marijuana or other drugs, but there is no test to accurately measure how intoxicated a person is after using any substance besides alcohol. You can be charged with a DUI, even if you have not consumed alcohol, if the officer believes you were under the influence of another substance.
It does not matter if there is no amount of alcohol in your system or if the drug was legal or even prescribed to you by a doctor. If the officer believes a substance affected your driving abilities, you can be charged with a DUI. A drug DUI charge can be particularly complex and require experienced lawyers because the case will essentially come down to whether or not you used a substance that could affect your ability to drive and if your driving was, in fact, affected by the substance.
If you have been accused of Driving Under the Influence of any substance, immediately contact a lawyer with experience fighting drunk driving cases and BAC results. Attorney Peter M. Liss has over 40 years of experience helping people in San Diego, California, fight their blood or breath BAC results/ He can help you too. Call (760) 643-4050 for a free consultation.
