California law criminalizes driving while drunk or high because alcohol or drugs impair a person’s mental or physical abilities to an extent they cannot operate a vehicle as cautiously as a sober person would. But how do the authorities tell that you are drunk or high? The state’s law has devised rules that hold every driver to the same standard that depends on blood alcohol concentration. If your blood alcohol concentration is above or at the stipulated standard limit, you could face DUI prosecution.

However, it is not final that if your blood alcohol concentration is at or above the standard limit, you are criminally liable for DUI. The test results could be false because of one mistake or another on the part of the test administrator. Therefore, you can contest the results to prove your innocence. To challenge BAC test results, you need assistance from an experienced DUI defense lawyer.

At San Luis Obispo DUI Attorneys, our lawyers understand what procedures must be complied with when determining blood alcohol concentration to obtain accurate results. If you have been arrested for or charged with drunk driving in San Luis Obispo, call us for help. We will not only help you with the blood alcohol concentration issue but also fight the entire DUI charges against you.

Blood Alcohol Concentration Overview

Blood alcohol concentration, abbreviated as BAC, is the alcohol quantity in somebody’s blood. Blood alcohol concentration is also called blood alcohol content/level and is expressed in percentage form, such as .08%, the state’s stipulated limit for many adult drivers. The percentage usually represents how many grams of alcoholic beverage can be detected in every one hundred milliliters of somebody’s blood.

So many grams show the individual’s system has a lot of alcohol. And if the number of grams is lower, the alcohol is less. A blood alcohol level can be calculated directly using blood testing. Alternatively, it may be estimated by breath testing.

BAC tests are deemed scientifically accurate in determining blood alcohol. Moreover, they are admissible in court as evidence when a person is accused of DUI.

Laws Regarding BAC

By law, anybody who operates a vehicle with a higher than a given BAC level is deemed intoxicated. This is called DUI per se. Per se means in itself. Some DUI cases are considered per se since having a BAC above or at the stipulated limit is a law violation. In this case, the D.A. does not have to prove the defendant’s driving was alcohol or drug-impaired. The following are the BAC levels for per se DUIs in California.

BAC Laws for Adult, Non-Commercial Drivers

Under state law, specifically VC 23152(b), it is unlawful for adult, non-commercial motorists to drive an automobile when they have a blood alcohol content of .08% or more measured by weight.

BAC Laws for Underage Drivers

California has two primary statutes governing the BAC level of under 21 drivers who drive while intoxicated. These are VC 23136, the state’s zero tolerance law, and VC 23140, underage DUI. The zero-tolerance law is particularly harsh on underage drivers. According to this law, a person below 21 years is prohibited from driving with a BAC of .01% or higher. Therefore, any detectable alcohol that appears on testing equipment would indicate the driver has violated the zero-tolerance law.

Under VC 23140, it is unlawful for a person under 21 years to drive a vehicle with a blood alcohol content of 0.05% or more. An underage motorist violates VC 23140 or VC 23136 merely by driving with the applicable BAC. Therefore, these laws can apply even if the motorist’s driving is not impaired.

BAC Laws for People on DUI Probation

Like motorists under 21 years, California DUI law also sets a BAC of 0.01% for defendants who have pled ‘no contest’ or ‘guilty’ to DUI and have been sentenced to probation. If the prosecutor proves you were serving your probation sentence and drove with any detectable alcohol quantity in your bloodstream, your license could be suspended for a year.

BAC Laws for Commercial Drivers

VC 13252(d), the state’s commercial DUI statute, makes it an offense for a person to drive a commercial motor vehicle with a BAC of 0.04% or more. The BAC limit applies only when a motorist operates a commercial motor vehicle. When a driver is driving a non-commercial vehicle, the standard stipulated BAC limit of 0.08% applies. Apart from commercial vehicles, the 0.04% or higher BAC applies to taxi, ride-sharing, limo, Uber, and Lyft drivers.

A BAC of .15% or Higher

Even for first-time DUI offenders, the law imposes severe punishment for anyone who drives with a BAC of .15% or more. 0.15% is close to double the stipulated limit of .08%. The prosecuting attorney can seek more severe consequences in this case than they would if the BAC was 0.08% because the driver has increasingly placed the lives of other road users in danger.

BAC Measurement

Blood alcohol concentration is determined by DUI breath or blood tests. These tests are deemed reliable if appropriately administered and admissible as court evidence. Breath DUI tests are the most prevalently administered because they are less invasive and generate instant results. Breath tests fall under two categories— post-arrest arrests and pre-arrest tests, called PAS (preliminary alcohol screening).

Pre-arrest tests are usually administered before an individual is detained for driving under the influence. This generally occurs at a sobriety checkpoint or after a traffic stop. You may lawfully decline PAS testing unless you are below 21 or currently serving a probation sentence for DUI. Post-arrest tests are administered after your arrest, as we shall see later.

How Breath Tests Determine the Alcohol Amount in the Blood

Breath tests usually do not directly determine the alcohol percentage in somebody’s blood. Rather, they gauge the alcohol amount found in someone’s deep lung air. A breathalyzer then mathematically changes this quantity to an estimated equal percentage of blood alcohol using the partition ratio formula.

Partition ratios vary across parties and situations. However, California law sets this ratio at 2,100:1, meaning the alcohol quantity detectable in 2,100 ml of alveolar air is considered lawfully equivalent to the alcohol amount in 1 ml of blood.

Blood Tests

DUI blood tests usually directly calculate the alcohol amount in someone’s blood, making them highly accurate tests for calculating an individual’s BAC when appropriately conducted. Here, a state-licensed person takes your blood and sends part of it for analysis. Your lawyer may receive the BAC test results after several days.

One primary benefit of blood testing over breath testing is; part of the blood specimen can be stored, and the defendant’s attorney can request it and take it for independent testing.

Here is how it works: when you choose to undergo blood testing, your lawyer can bring a blood split motion. The motion enables the lawyer to obtain a portion of the blood specimen the authorities used and send it to a laboratory of their choice for an independent analysis. If the test results differ, your lawyer can utilize them to contest the D.A.s’ case.

Urine Tests to Determine BAC

Urine tests do not often calculate a blood alcohol level in DUI cases. Even though urine testing can accurately show alcohol presence, it is not as reliable as breath or blood testing for establishing a definite alcohol quantity present. Thus, urine tests can only be considered in California DUI cases if:

  • Breath and blood tests are unavailable.
  • The defendant cannot undergo one of the tests, and the other test is unavailable.

Reasons a defendant may be unable to take a breath or blood test include:

  • An immensely high degree of intoxication or unconsciousness, making it impossible or difficult to undergo breath testing.
  • A health-related condition, for example, a clotting disorder or breathing problem.

BAC Application In DUI Traffic Stops and Arrests

Police officers use blood alcohol content in two instants— during a a drunk-driving arrest and investigation. When a police officer pulls you over and suspects you are drunk or high, they may initiate an investigation for DUI. Part of this investigation may entail the officer asking you to submit to a pre-arrest PAS test.

Should you blow a BAC less than the standard limit, the law enforcement officer will let you go with only a warning or traffic ticket. And if the results are positive, the police officer may arrest you and require that you undergo post-arrest blood or breath testing.

If you believe your BAC may be above the stipulated limit, it is not in your best interest to take a pre-arrest PAS test. You could respectfully refuse to undergo the test. The law enforcement officer might still arrest you anyway. And if your blood alcohol content is lower than the stipulated limit, you may also refuse to take the PAS test. However, some motorists prefer undergoing testing to prove they are sober.

Post-Arrest Blood or Breath Tests

Once you have been legally arrested for driving while intoxicated, you will be granted the option of a blood or breath test. Although, if the arresting officer has reason to suspect you are high, they may demand to test your blood apart from or instead of a breath test.

Post-arrest blood and breath test results are deemed evidentiary, meaning they are admissible in court as evidence a motorist drove while intoxicated. You must take a post-arrest blood or breath test regardless of whether or not you submitted to pre-arrest testing. Refusing to take the tests may subject you to criminal penalties. The consequences for refusing to submit to post-arrest tests include driver’s license suspension for a minimum of 12 months.

Which Test Should I Choose Between Breath and Blood Test After Arrest?

Unluckily, it is not easy to tell what is the ideal chemical DUI test to choose after being arrested. Each of these tests has its independent benefits and drawbacks. Additionally, an experienced DUI attorney could challenge these tests in court.

The most critical move is to stay as respectful to the arresting officer as possible and avoid talking too much. BAC results are not the sole evidence the prosecution can utilize to seek conviction for DUI. The police might also testify regarding what you said and how you said it.

Breath and Blood Test Advantages

Most people caught drunk driving opt to undergo breath testing because the results can be available immediately, and the test is minimally invasive and not stressful.

After arrest, breath tests are usually administered at the police station and on a desktop machine. Otherwise, they are similar to PAS tests. In a few counties, the arresting officer may administer the post-arrest breath test by the roadside. If that is the case, the test will be similar to the pre-arrest PAS test, with only one critical difference. The difference is that, unlike PAS tests, post-arrest tests are not optional, regardless of where they are administered.

The primary advantages of DUI blood tests are:

  • A portion of the specimen can be stored and tested independently by a laboratory of the motorist's choice. Breath samples cannot be preserved.
  • A blood specimen enables a BAC evaluation that is more accurate than breath samples. This could come in handy when a person’s BAC is very close to the lawful limit.

Benefits of Refusing a Chemical DUI Test

The one benefit of declining to undergo chemical testing is the prosecution or police officer will have no way of proving your BAC. This may help you avoid prosecution for DUI. The D.A. will need to show guilt by proving your driving was impaired by drugs, alcohol, or both.

However, refusing to undergo chemical testing itself is evidence of criminal liability. Additionally, you will face penalties for chemical test refusal, such as:

  • Automatic license suspension by the DMV for a minimum of 12 months.
  • Additional jail time if you are eventually convicted of DUI.
  • DUI school for nine months (rather than the usual three months) if you are ultimately found guilty.

Regardless of the penalties for a chemical DUI test refusal, it may be an ideal choice if:

  • You are very intoxicated and do not want to be subject to the additional repercussions of operating a vehicle with a very high BAC (0.15% or more).
  • You do not rely on driving to move around (and can thus afford to be subject to the automatic license suspension penalty).

However, remember that if you have a very high blood alcohol content, you may not be able to make the best decisions at that moment. Irrespective of your decision, it is good to consult a skilled DUI lawyer as soon as possible afterward.

Title 17 Regulations as They Apply to Post-Arrest Tests

Title 17 provides strict procedures for breath or blood testing after a DUI arrest. A knowledgeable DUI defense attorney can dispute the BAC results if these procedures are not followed exhaustively. Some of the most critical Title 17 requirements for breath and blood tests are:

  • An authorized person must draw the blood sample.
  • The breath sample must come from deep lung air.
  • The blood specimen must be stored properly.
  • The test administrator must observe the individual providing the breath sample for a minimum of fifteen minutes before they give the specimen.
  • An alcohol-based cleaning agent must not be utilized to sterilize the draw site.

BAC Application During DUI Prosecution

In DUI cases, the prosecution will use blood alcohol content and other additional evidence to show the motorist either was above the lawful limit and thus criminally liable for a per se DUI or impaired and thus guilty of DUI.

As mentioned earlier, a per se DUI depends on an objective impairment measurement. If the blood alcohol content is above/at a specified limit, a motorist is legally deemed too impaired to drive.

Driving while intoxicated is a subjective test, meaning the prosecuting attorney must prove the motorist was incapable of driving safely because of alcohol.

Blood alcohol concentration is only one element of a subjective DUI prosecution. The higher the BAC level, the higher the chances you drove while impaired. However, more evidence to suggest impairment is often required. This evidence might include the following:

  • The arresting officer's testimony about physical intoxication signs and vehicle driving pattern.
  • Other witnesses' testimony, including any passenger who was in the car.
  • Evidence of the time you drove.

Fighting BAC Results in a Court of Law

Just because the test results show you have a particular BAC does not imply they are correct. These tests can have various errors. An experienced DUI lawyer can use these errors to challenge the results. The lawyer can argue that:

  • You were on a low-carb or high-protein diet.
  • The arresting officer failed to properly advise you of the consequences and choices involved in submitting to DUI chemical testing.
  • The arresting officer failed to follow proper procedures when giving the chemical DUI tests.
  • The testing equipment was not calibrated correctly, as the state’s law requires.
  • The blood or breath specimen was mishandled; therefore, it may be contaminated.
  • You had rising blood alcohol when you underwent testing, meaning your blood alcohol concentration was lower while driving.
  • There was residual mouth alcohol in your mouth.
  • You suffer from a health condition like diabetes or GERD, leading to a false BAC reading.

Contact a Competent DUI Defense Lawyer Near Me

If you fail your BAC test, it is not the end of the road. An expert DUI defense attorney can help you challenge the results. At San Luis Obispo DUI Attorneys, we are intimately conversant with issues that lead to incorrect BAC results, and we are prepared to use them to our advantage to fight for you aggressively.

We know what strategies to apply to defend you effectively, as we have successfully defended hundreds of our clients in their drunk driving cases. Regardless of the circumstances surrounding your arrest, we are ready to help you regain your freedom and driving privilege. Call us at 805-321-1000 for a consultation.