California DUI law imposes alegalBAC limitfor most adult drivers of.08% blood alcohol concentration. However, the law imposes an even lower limit for commercial, taxi, limo, rideshare and underage drivers.

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Specifically, the limits are:

Adult chauffeurs (non-commercial vehicles): .08%.1 commercial drivers: .04%.2 Taxi, limo, and ride-sharing drivers: .04%.3 Underage drivers: .05%.4

Can who be under the influence with a BAC listed below California’s “legal limit”?

Someone have the right to be uncovered guilty of steering under the influence even if his or she BAC is under the “legal limit.” A person is taken into consideration to be under the affect (regardless the BAC) anytime that:

due to the influence of alcohol and/or drugs, the person have the right to no longer drive as well as a careful sober person under similar circumstances.5

To assist you better understand the law, ours California DUI defense lawyersexplain 8 an important points around BAC:

3. How is BAC measured? 3.1. DUI breath tests 5. How is BAC used throughout a DUI traffic stop and arrest? 7. Need to a driver pick a blood or a breath test if arrested because that a California DUI?


1. What is BAC?

Blood alcohol concentration (“BAC”) is a measure up of the amount of alcohol in a person’s bloodstream. It is also referred to together “blood alcohol content” or “blood alcohol level.”

BAC is expressed together a percent – for instance .08% (the California DUI border for many adult drivers). This percentage represents the grams of alcohol existing in every 100 milliliters that someone’s blood.

A greater number indicates that a person has an ext alcohol in his or she system. A reduced number indicates less alcohol.

BAC have the right to be measured directly by a DUI blood test. Or it can be approximated through a DUI breath test. We discuss these in ar 3, below.

2. Exactly how accurate room BAC measurements?

DUI chemistry tests for BAC are taken into consideration a scientifically accurate method to measure up blood alcohol. Much more importantly, they room legally admissible as proof in a California steering under the influence prosecution.

3. Exactly how is BAC measured?

BAC is measure by either a DUI breath check or a DUI blood test. Both are thought about reliable when properly administered. Both are admissible in court.

Let’s take it a closer watch at every of them.

3.1. DUI breath tests

The most generally used test for BAC in California is a breath test. Breath tests are minimally invasive and also deliver prompt results.

Breath exam in California fall into two basic categories (discussed below):

Post-arrest DUI breath tests. exactly how DUI breath tests measure up blood alcohol

A breath check does not straight measure the percent of alcohol in someone’s blood. Instead, it steps the alcohol current in the deepest component of someone’s lungs, wherein it is closest to the individual’s blood supply.

A “Breathalyzer”-style maker then mathematically converts this amount right into an around equivalent blood alcohol percentage. The formula it uses to carry out this is known as a “partition ratio.”

In actual fact, partition ratios have the right to differ from person to person and situation to situation. Yet in California, by law, the partition proportion is reputed to be 2,100 to 1.6 This way that the quantity of alcohol current in 2,100 milliliters that deep lung breath is considered legally same to the lot of alcohol in 1 milliliter of blood.


3.1.1 Preliminary alcohol screening (PAS) exam

A preliminary alcohol displays (PAS) check is usually given before someone is arrested for DUI. Typically, this will take place after a traffic prevent or in ~ a DUI sobriety checkpoint.

A pre-arrest PAS test may lawfully be declined by a driver unless:

The driver is under 21 year of age,7 or The driver is ~ above probation because that a front DUI offense.8 3.1.2. Post-arrest DUI breath test

After a driver has actually been lawfully arrested because that DUI, he or she will be provided the an option of a breath or blood test. The driver must take this test even if he/she previously took a PAS breath test. 9

Consequences the refusing to take a chemistry test incorporate the automatically suspension the the driver’s patent for at the very least one year.10

Most human being elect to take the breath test as it is much less invasive. This post-arrest breath check is usually provided on a desktop device at the police station. Otherwise, it is comparable to a PAS test.

In some counties, the police may offer this post-arrest breath test roadside. In this case, it will certainly appear comparable to a PAS test. The necessary difference, however, is that unlike a PAS test, a post-arrest check is not optional, no matter where it is given.

3.2. DUI blood tests

Blood tests straight measure the alcohol in a person’s blood. This provides them the many accurate test because that determining a person’s blood alcohol concentration—at least, when whatever is excellent strictly follow to the procedure.

The driver’s blood will be taken by who licensed by the state.11 component of this sample will be sent out to a lab for analysis. It deserve to take several weeks because that a driver’s lawyer to obtain these check results.

The main benefit of a DUI blood test over a DUI breath check is that component of the sample deserve to be saved. This means the driver’s lawyer can gain ahold of it and have it separately tested.12

As Riverside DUI defense attorney Michael Scaffidi13 explains,

“When a client chooses a blood test, us can paper a California DUI ‘blood split’ motion. This lets us obtain part of the same blood sample the police used and have it sent out to a lab of our an option for elevation testing. If the outcomes are different, we can frequently use lock to challenge the prosecution’s case.”

3.3. Deserve to BAC be measured through a urine check in California?

Blood alcohol concentration is not generally measured by a urine check in California DUI cases. Urine tests deserve to accurately finding the visibility of alcohol. But they are less reliable 보다 blood tests of breath tests for determining the specific amount the alcohol present.

So a urine test will only be offered in a California drunk driving instance if:

Both a blood and also breath test room unavailable, or The human being arrested is i can not qualify of taking among the tests and the other one is no available.14

Reasons an individual might be i can not qualify of acquisition a blood or breath test deserve to include:

A medical condition (such as a breath disorder or clotting disorder), or an extremely high level that inebriation or unconsciousness (making it difficult or impossible to complete a breath test).


4. What is the legal border for BAC in California?

By law, anyone who drives with a much more than a particular amount of alcohol in his or her system is taken into consideration to it is in under the influence. This is recognized as a “per se” DUI under the car Code sections collection forth below.

“Per se” is a Latin phrase definition “in itself.”15 part DUIs are “per se” since having a BAC in ~ or above theCalifornia DUI border is thought about a violation of legislation in and of itself. In such a case, the prosecutor does not need to prove the the person’s driving was in reality impaired.

California’s “per se” DUI password sections

California’s “per se” DUI password sections are:

California likewise has two “zero tolerance” laws. Violation is technically not a DUI and also compliance deserve to be measured by a PAS test. These two laws are:

Drivers under 21 or who are on DUI probation hurt these laws by driving through a BAC that .01% or higher. That human being can likewise be charged with DUI if BAC is measure at any type of higher, applicable level (which will certainly be confirmed with a post-arrest blood or breath test).

5. How is BAC used throughout a DUI website traffic stop and arrest?

BAC is supplied by legislation enforcement at two different stages:

The DUI investigation, and also The DUI arrest.

Learn much more about these stages in our article, “The Court process in California DUI Cases.”

5.1. Blood alcohol measurements during a DUI investigation (“PAS” test)

During a website traffic stop, if the officer doubt a driver of being under the influence, he/she may start a DUI investigation. As part of the investigation, the officer may ask the driver to take a PAS test.16

If the driver “blows” a BAC listed below the legal limit, the officer will typically let the person go with just a traffic ticket or a warning.

If the test is positive, the officer will more than likely arrest the driver and also require a post-arrest breath or blood test.

have to a driver agree come a PAS test?

An adult driver who thinks he/she may more than the legal border is not normally well-served by acquisition a PAS test. That or she can (and most likely should) politely decrease to take it one. The officer might arrest the person anyway.

Someone that is under the legit limit likewise has the best to decline. Some chauffeurs prefer, however, to take the check in order to present the officer that they room not drunk.

Note that drivers who space under the period of 21 or ~ above DUI probation might not refuse a PAS without consequences.17


5.2. Post-arrest breath or blood tests because that blood alcohol

A post-arrest chemical check is considered “evidentiary.” This way a prosecutor deserve to use the in court come as evidence that a driver drive drunk.

This form of chemistry test may not be refused by a driver there is no consequences.18

The driver must usually be available the selection of a breath or blood test. 19 yet in some cases, the officer deserve to require testing of the driver’s blood. This have the right to be rather of (or in enhancement to a breath reading) if the officer sensibly believes the driver is under the affect of drugs.20

5.3. Title 17 procedures and also chemical tests for alcohol

Title 17 of the California code of regulation sets soon strict measures for DUI chemistry tests.

If these measures are not adhered to to the letter, an experienced California DUI defense lawyer can difficulty the results.

We talk about such challenges in section 8, below.

6. How is BAC used during a California DUI prosecution?

During a California DUI case, the prosecutor will usage BAC and also other proof to prove the the driver either:

to be over the legal border and, therefore, guilty the a DUI per se, or to be actually impaired and, therefore, guilty of driving under the influence.

DUI every se counts on an “objective” measure of impairment. If BAC is at or above a mentioned level (such together .08 for an adult in a non-commercial vehicle), a driver is legally considered too drunk to drive.

Driving under the influence is a “subjective” test. The prosecutor must present that the driver was unable to journey safely because of alcohol.

BAC is just one element of a “subjective” drunk steering prosecution. The greater a driver’s BAC, the an ext likely that the person was impaired. But additional evidence of handicap is usually required.

Such other evidence could include:

Testimony from the arresting officer about driving pattern and physical symptom of intoxication, evidence of as soon as the driver drove, and Testimony from various other witnesses (including passenger in the vehicle, if any).


7. Should a driver select a blood or a breath check if arrested because that a California DUI?

Unfortunately, there is no straightforward answer as to the best chemical test to choose after a DUI arrest. Each has actually its advantages, as debated below. Each can be challenged by an competent California drunk control lawyer.

The crucial thing is come be together polite as possible to the officer and to speak as little as possible. A chemical test is not the only proof that can be supplied to convict someone of control under the influence. The officer may additionally testify around what the driver says and how he or she says it.

7.1. Benefits of a California DUI breath test

Most world arrested because that DUI choose to take a breath test. The main benefits of a breath BAC measurement space that:

that is less invasive and less stressful for most people, and also The results are obtainable right away.

7.2. Benefits of a California DUI blood test

The main benefits to a DUI blood test are that:

A blood sample allows a more accurate assessment of BAC than a breath same. This have the right to be beneficial when someone is an extremely close to the legitimate limit). Component of the blood sample deserve to be saved and also independently tested by a rap of the driver’s choosing. Breath samples room not preserved.

7.3. Benefits of a chemical check refusal

The one benefit to refusing a chemical test is the there will certainly be no way to prove the driver’s BAC. This have the right to be helpful to prevent a criminal prosecution because that drunk driving.

The prosecution will need to prove guilt by showing that the defendant’s control was in reality impaired by alcohol and/or drugs.

But… a refusal to take a chemical check is itself admissible as proof of guilt.21 (Note that this does not apply to a PAS test uneven the driver is under 21 or on DUI probation).22

And the driver faces consequences for check refusal, including:

automatically suspension the the driver’s patent by the California DMV for at the very least one year, added time in jail if the driver is ultimately convicted of driving under the influence, and also who might advantage from a chemical check refusal?

Despite the aftermath of a refusal, it can be a great choice if:

The driver does not depend on driving come get approximately (and can, therefore, bought to endure the automatically driver’s license suspension), and/or The driver is very drunk and also does want to endure the additional consequences the driving with a an extremely high BAC (.015% or higher).24

But save in mind the a driver through a an extremely high BAC can not be qualified of make the ideal decision in the moment.

Regardless the the decision, a driver in this position makes, the is a an excellent idea come consult an proficient California drunk driving attorney as shortly as feasible afterward.

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8. How deserve to a driver fight DUI test results in court?

Just since a breath or blood test showed a specific BAC, that doesn’t typical the results were accurate.

We discuss potential errors at size in our write-ups on:

But in general, BAC results have the right to be tested by acquisition one or an ext of the adhering to positions:

The officer walk not correctly advise the driver that the options and consequences involved in acquisition DUI chemistry tests; The officer did no observe appropriate procedures throughout the administration of the DUI test; The testing tools was not calibrated as required under California law; The breath or blood sample to be mishandled and possibly contaminated;

For more information, please see our article, “20 legitimate Defenses because that Fighting California DUI Charges.”

Arrested for DUI in California? speak to us for help…

California vehicle Code 23152(b). Automobile Code 23152(d). Auto Code 23152(e). Automobile Code 23140 VC. Auto Code 23152(a). Automobile Code 23152(b) vehicle Code 13388 car Code 23612(a)(1)(A) car Code 23612(a)(1)(D). Auto Code 23158(a).See additionally 7 California code of regulations § 1219.1(a): “Blood samples shall be built up by venipuncture native living individuals as soon as feasible after an alleged offense and only by persons authorized by section 23158 the the car Code.” automobile Code 23158(b) VC. Riverside DUI defense lawyer Michael Scaffidi is a former police officer and also police sergeant who now uses his inside understanding to defends clients accused the DUI and also other criminal offenses throughout mountain Bernardino and also Riverside Counties. Car Code 23612(a)(2)(A), endnote 9. See, e.g.,, definition of “per se.” vehicle Code 23612(a)(2)(A), endnote 9. Auto Code sections 13388 and also 13389. Vehicle Code 23612(a)(1)(A), endnote 9. Automobile Code 23612(a)(2)(A) vehicle Code 23612 (a)(2)(C) VC. See, e.g., California Criminal Jury indict (CALCRIM) 2130. Refusal – awareness of Guilt. automobile Code 13353