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Difference Between BAC and Zero Tolerance in DUI Cases?

Posted by Dmitry Gorin | Oct 21, 2022

There is understandably a bit of confusion among California drivers as to whether or when they can be charged with Vehicle Code 23152 VC driving under the influence.

On the one hand, most people familiar with DUI understand that California recognizes a blood alcohol concentration (BAC) of 0.08 as the legal threshold for being "under the influence."

Blood alcohol concentration (BAC) measures the amount of alcohol in someone's bloodstream and is often called “blood alcohol level.”

Difference Between BAC and Zero Tolerance in DUI Cases
The blood alcohol concentration (BAC) measures the amount of alcohol in somebody's bloodstream.

BAC is expressed as a percentage, such as .08%, the legal limit in California. This percentage refers to the grams of alcohol present in every 100 milliliters of a person's blood.

A higher number indicates that someone has more alcohol in their system, while a lower number means less alcohol. BAC can be measured directly by a DUI blood test or estimated by a DUI breath test.

There are two categories of breath tests: the pre-arrest “preliminary alcohol screening” (PAS) tests and the post-arrest DUI breath tests.

DUI chemical tests for BAC are generally considered scientifically accurate in measuring blood alcohol. Further, the results are legally admissible as evidence in a driving under the influence prosecution in California.

On the other, they've heard about the "zero tolerance" policy in which they could be arrested if alcohol is detected in their system. What is the difference between these two policies, and how do you know which one applies to your case if you've been arrested on suspicion of DUI?

In short, both refer to the amount of alcohol in your system, but they are two different standards designed to fit other circumstances. Let's take a closer look at BAC versus zero tolerance, the differences between them, and which one could be applied to your situation.

What is the Blood Alcohol Content Standard?

For most California drivers, the BAC standard applies in most cases. This means that if a police officer pulls you over and arrests you on the suspicion that you are impaired, you can be charged with DUI if your blood alcohol content is at or above the "legal limit."

For most drivers, the legal limit is a BAC of 0.08; for commercial drivers, it is 0.04. The officer usually measures the BAC via a Preliminary Alcohol Screening (PAS) or using a breathalyzer, which you have the right to refuse unless you have already been arrested.

If the officer does arrest you, you must submit to either a PAS or blood test or face automatic suspension of your license, regardless of the outcome.

Generally, testing below the legal limit means you won't be charged. However, there are two caveats to consider:

  • You can be impaired while below the legal limit and still be arrested and charged with DUI. This is partly because California's DUI laws also apply to drug use, which isn't detectable via a PAS. Another reason is that some people are more sensitive to alcohol and may be impaired even if their BAC is below the legal limit. If the officer suspects you are impaired, they can arrest you with or without a BAC screening. If your BAC is below the legal limit, you can still be charged with a DUI if the prosecutor can show that your driving ability was impaired by the alcohol you consumed.
  • You can be charged with DUI if you test above the legal limit—even if you show no impairment. In other words, if law enforcement can detain you regardless of how (or if) you test, the legal threshold is the law, and violating it is a crime.

What is the Zero Tolerance Law in California?

There are two specific California instances where the zero tolerance laws apply—meaning you can face penalties if any amount of alcohol is detected in your system. Zero tolerance applies specifically to drivers under age 21 and those currently on DUI probation.

Drivers Under Age 21 

According to Vehicle Code 23136 VC, it is illegal for anyone under 21 to drive with any measurable amount of alcohol in their system (generally, BAC 0.01).

California's Zero Tolerance Law
The Zero Tolerance Law includes drivers under 21 and anyone who is on probation for DUI.

If you're under age 21 and a police officer pulls you over and detects even a small amount of alcohol via a PAS, you can have your license suspended.

Bear in mind that VC 23136 is a civil offense, not a criminal one, so violating it won't result in DUI charges on its own—just the loss of your driver's license.

But if your BAC exceeds 0.05, you can still be charged with DUI on top of the violation of the zero-tolerance law. Also, as an underage driver, you don't have the right to refuse a PAS if the officer wants to give you one.

Drivers on Probation for DUI

Suppose you have been convicted of DUI in California and are on summary probation for that offense. In that case, you are also subject to the zero tolerance laws as a term of your probation under Vehicle Code 23600 VC.

The probation is typical “summary probation,” meaning you don't have to check in with a probation officer and are not monitored regularly.

If you are on DUI probation and are pulled over and the police suspect you are impaired, here's what happens:

  • You must submit to a PAS test as part of your probation. If you refuse, your probation is revoked;
  • If alcohol is detected in any amount, your license is automatically suspended for one year;
  • If you test at BAC 0.04 or higher, it's a violation of your probation, and you may face having your probation revoked.

Regardless of what type of DUI you face, you must defend yourself. Any DUI conviction can carry life-altering consequences on your personal and professional life. If you have prior DUIs, the penalties are even harsher.

Put simply; you will need an experienced DUI attorney who knows how to minimize the impact a DUI can have on your life. Perhaps the charges can be reduced or dismissed after negotiations with the prosecutor.

Eisner Gorin LLP is located in Los Angeles, California. You can contact our law firm for an initial case consultation by phone or using the contact form.

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About the Author

Dmitry Gorin

Dmitry Gorin is a licensed attorney, who has been involved in criminal trial work and pretrial litigation since 1994. Before becoming partner in Eisner Gorin LLP, Mr. Gorin was a Senior Deputy District Attorney in Los Angeles Courts for more than ten years. As a criminal tri...

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