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BAC Limit in California

BAC or “blood alcohol concentration” is the unit of measurement used in determining the amount of alcohol a person has in their system. It is shown in percentages, representing how many grams of alcohol may be found in every 100 milliliters of blood.

In California, the law sets a legal limit for drivers and the legal limit varies depending on whether you are an adult driver or if you drive a vehicle as a profession. The specific BAC limits are as follows:

  • Non-commercial adult drivers = 0.08%[1]
  • Commercial drivers (Ex. Delivery service drivers, etc.) = 0.04%[2]
  • Those who take “passengers for hire” (Ex. taxi drivers, ride-sharing drivers) = 0.04%[3]
  • Underage drivers = 0.05%[4]

DUI even if BAC is below legal limit

With the legal limit for BAC being set in California, it is still possible to be arrested and charged with a DUI even if your BAC is below the legal limit. To be found guilty of a DUI (below legal limit), the prosecution needs only prove two things:

  1. You drove a vehicle
  2. When you were driving, you were under the influence of an alcoholic beverage or a drug or a combination of both

The reason for this is that the law considers you as someone “under the influence” if, as a result of drinking or taking drugs, your driving was impaired.

If you are arrested for being on or above the BAC legal limit, you will be charged with a “DUI per se”. This means that even if your manner of driving was not impaired, just driving while having a BAC on or above the legal limit is already considered a punishable crime. A DUI per se will incur higher and stricter penalties.

When is BAC measured?

There are various methods for determining BAC. In the context of a DUI, BAC will be measured at two different points: 1) prior to the arrest called “preliminary alcohol screening” (otherwise known as PAS test); and 2) after an arrest has been made.

Preliminary alcohol screening or PAS test is usually conducted after a traffic stop but at which point, no arrest has been made yet. This test is specifically conducted by the arresting officer when they suspect that a driver might be under the influence. A driver may lawfully decline to take this test. However, there are certain drivers that may not decline and have to comply, particularly: 1) drivers under the age of 21; and 2) drivers on probation for a prior DUI.

A Post-arrest test is conducted after a driver has been lawfully arrested for a DUI. The results of this test can be used in court as evidence. A driver arrested for DUI will be required to take a chemical test (choice of a breath test or blood test). Take note that refusing to take the chemical test at this point will have major consequences which include:

  • increased penalties on top of standard DUI penalties
  • a mandatory driver’s license suspension (regardless of the outcome of the DUI case)
  • can be used as evidence for admission of guilt

What are the different types of BAC tests for DUIs?

In California, BAC is measured through the use of a breathalyzer or by taking a blood sample. There are advantages and disadvantages in both tests and choosing the “better” one will depend on the circumstances. If you have been arrested or charged with a DUI, it is always a good idea to consult with an experienced DUI defense lawyer as soon as possible.

  1. Breath Test – A breath test is usually taken with a “breathalyzer”. A breathalyzer is a machine that measures the alcohol from the deepest part of a person’s lungs instead of the blood. The breathalyzer then converts the reading to an approximate equivalent in blood alcohol percentage. In California BAC is measured by grams of alcohol per 100 milliliters of blood or grams of alcohol per 210 liters of breath.[5] This test is non-invasive and the results are immediate, provided that that you were able to give a deep-lung breath sample. The downside of a breath test is that you cannot have independent testing done considering that no samples can be stored.
  1. Blood Test - A blood test directly measures the amount of alcohol in the blood. In terms of a DUI, the one taking the blood sample should be a person that has been legally authorized by the state to take such sample. Part of the sample taken will be sent to a laboratory for analysis while the remainder is set aside for the driver. The reason behind this is so that the driver will have an opportunity to have independent testing done. Your attorney can file in court a “blood split motion” so that you can obtain the remaining blood sample and have an independent laboratory conduct the testing. The downside of taking the blood test is that the procedure is invasive (a needle is used to take blood from your arm) and the results take a long time to be processed.

Take note that urine testing is not a primary mode for testing BAC in California. It will only be done in cases when:

  • Breath test or blood testing is not available
  • An arrested driver incapable of taking one of the tests (either due to a medical condition or extreme cases of drunkenness) and the other test is unavailable

California Code of Procedures Title 17

This law sets forth strict procedures in terms of who can conduct BAC tests and how testing should be conducted, calibration of equipment, among others. Failure to follow these procedures can greatly affect the results of a DUI case.

What are the possible defenses against BAC test results?

BAC test results are not always accurate and sometimes the manner by which it is obtained is contrary to the procedures set by law. Below is a list of some possible defenses. This list is not exclusive and may vary depending on the circumstances of the case:

  • The officer did not properly advise the driver of the type of tests and the consequences of taking the tests
  • The person conducting the test was not trained or authorized by the state
  • The person conducting the test did not observe proper procedure when the test was conducted, or failed to follow procedure in storing the test sample
  • The testing equipment was not calibrated according to the standards set by law
  • The driver was suffering from a medical condition that falsely elevated the BAC results (i.e. auto-brewery syndrome, acid-reflux, diabetes, etc.)
  • At the time the driver took the wheel, he or she was not under the influence (i.e. “rising blood alcohol”, etc.)

No Judgment, Only Professionalism

If you have been arrested or charged with a DUI, it is all-important to hire an experienced, aggressive, and seasoned private West Covina defense lawyer to fight your case. We always make our clients feel right at home and we encourage you to take comfort in the fact that you have a dedicated advocate on your side at Coimbra Law Firm, APC. Our highly-experienced lawyers at Coimbra Law Firm, APC will help ensure that your Constitutional rights are protected. Each of our clients will receive personalized attention, complete discretion, and trained staff working to provide the best legal assistance available. Our only job is to defend you with the maximum competence, diligence, and zealousness. Do not hesitate to call (626) 827-7222 for the representation you need.


[1] California Vehicle Code § 23152 (b)

[2] California Vehicle Code § 23152 (d)

[3] California Vehicle Code § 23152 (e)

[4] California Vehicle Code § 23140

[5] Supra note 1.

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