Your BAC level is one of the primary determining factors as to whether you will be prosecuted or convicted of a DUI. In the state of California, there are prescribed BAC limits that motorists should not exceed. The Prosecution Department of California will charge you of DUI if you exceed these limits. Read on to know more about how blood alcohol concentration affects DUI cases in California.

We at The DUI Defense Attorney have extensive experience in defending individuals charged with DUI in Van Nuys. Also, we have deep familiarity with all the local court processes applicable in this area. With us by your side, you have greater chances of a dismissal, or a reduction of your charges. Get in touch with us today to jumpstart your case.

What is BAC?

The term blood alcohol concentration (BAC) refers to the measurable alcoholic amount in the bloodstream of an individual. Other terms that are synonymous with blood alcohol concentration include blood alcohol level and blood alcohol content.

BAC is denoted in percentages. The percentage represents how many grams of alcohol are present in every 100 milliliters of a person’s blood. When a person has a BAC of 0.12%, it means that this person has 12 grams of alcohol for every 100 milliliters of his blood.

When this percentage is high, it signifies that the person has high levels of alcohol in his bloodstream. A low percentage implies that the individual has little alcoholic content within his blood. Individuals with high BAC levels are most likely to drive under the influence because they are not in the right state of mind.

How BAC is Measured

Law enforcement officers in California measure BAC using two tests; blood or breath tests. You can be subjected to these tests at the point of arrest or the police station after you have been booked.

Both of these tests are scientifically accurate, provided that they are appropriately administered. Also, both of them are admissible in court as evidence. Here is a detailed explanation of each of them:

Breath Tests

This is the most common test that California law enforcement officers utilize to measure BAC. A breath test is minimally invasive, and it can deliver results instantly. There are two categories of breath tests: Pre-arrest 'Preliminary Alcohol Screening' (PAS) tests and post-arrest tests.

How Does a Breath Test Measure BAC?

Breath tests do not measure the total amount of alcohol directly in a person's bloodstream. Instead, they measure the amount of alcohol present in the deepest area of an individual’s lungs, which is in proximity to the blood supply of that individual.

Typically, breath testing kits resemble breathalyzers. These kits convert the alcohol amount present in the lungs to an equivalent blood-alcohol percentage using the partition ratio formula.

The partition ratio may vary from one person to another and depending on the situation. According to California DUI laws, this ratio is 2100:1. This ratio implies that the 2100 milliliters of alcohol present in the deepest area of an individual's lungs is equivalent to the total amount of alcohol present in 1 milliliter of an individual’s bloodstream.

Pre-arrest/Preliminary Alcohol Screening (PAS) Breath Tests

A law enforcement officer may subject you to the PAS test before arresting you for DUI. Most pre-arrest tests occur at DUI sobriety checkpoints or traffic stops. You have a right to lawfully decline to take these tests unless you are below 21 years old, or if you are serving a probation term because of a prior DUI conviction.

Post-arrest Breath Tests

After the law enforcement officer has arrested you for a DUI, he may subject you to a post-arrest breath test. You may be put under arrest for driving under the influence if a police officer notices that you manifest any physical signs of intoxication. You will be taken to the police station after you have been arrested for booking. Most post-arrest breath tests take place in police stations.

Post-arrest tests are non-optional, and you may face severe legal consequences if you refuse to submit to them. Since these breath tests are non-invasive, there is nothing for you to lose if you take them. However, some specific circumstances can permit you to refuse to accept a post-arrest DUI test, or make you accrue some advantages when you fail to submit to the test. You shouldn't worry when the breath testing kit indicates a high BAC because your attorney will find a way out to defend you and have your charges reduced or become acquitted.

Blood Tests

Unlike breath tests, blood tests measure the total amount of alcohol present directly in an individual's bloodstream. Blood tests are highly accurate when they are correctly administered.

A state-licensed officer will take a sample of your blood and test it in a medical laboratory. You may take a couple of weeks to know the results.

Part of your blood sample will be saved, and your attorney can access it and get it tested independently. If he/she finds different results, he/she can utilize them to challenge the prosecutor’s case.

The Admissibility of Urine Tests in California Courts

Urine tests are not admissible as evidence in California DUI cases, though they are scientifically accurate. Since courts do not admit them, California law enforcement officers rarely use them. Although urine tests are scientifically accurate, they are not reliable.

A California court can only permit a urine test to be used in a DUI case in circumstances where both breath and blood tests are unavailable, and the accused person is unable to take either a blood or breath test or the other test is unavailable. An individual may lack the capacity to submit to a blood or breath test because of his medical condition or a high level of unconsciousness or inebriation.

The Prescribed BAC Legal Limits in California

The DUI laws of California have enlisted prescribed BAC limits, which all motorists should observe. These limits vary depending on the age of the driver and the vehicle type he/she is driving.

Adult drivers of non-commercial vehicles should not exceed a BAC of 0.08%. On the other hand, drivers of commercial vehicles should not have a BAC of 0.04% or higher. Teenagers and individuals who are serving a probation term should not have any detectable amount of alcohol in their blood system when driving, as illustrated by California's zero-tolerance DUI laws.

If you exceed any of the prescribed BAC legal limits, the prosecution may charge you with 'per se' DUI. 'Per se' is a Latin term that means 'of itself.' Therefore, if the prosecution charges you with per se DUI, it means that you have committed an actual violation of California DUI laws, and the prosecutor has no obligation to prove that you drove while you were impaired.

Can I Still Be Arrested for DUI if my BAC does not Exceed the Prescribed Legal Limits?

Yes, you can still be arrested for DUI even if your BAC does not exceed the prescribed legal limits. In fact, the court can find you criminally liable for driving under the influence if the prosecution proves that you were indeed intoxicated, regardless of your BAC level.

Typically, a law enforcement officer will flag you down if he believes that you are driving recklessly or violating a traffic law. When you pull over, you may be subjected to a field sobriety test. The officer will look out for the physical symptoms of intoxication, including a lack of focus and concentration, sluggish behavior, red eyes, and alcoholic breath, among others. This officer may put you under arrest for DUI if he believes that you are not sober.

How BAC is used during DUI Traffic Stops and Arrests

Often, law enforcement officers use BAC during investigations and arrests at traffic stops or DUI sobriety checkpoints. As a motorist in California, you should pull over when you reach a traffic stop or sobriety checkpoint. 

When you pull over, a police officer will approach you. If the officer suspects you to be under the influence, he will launch a DUI criminal investigation. He will request you to take a PAS breath test during the investigation process. If he finds out that your BAC exceeds California's legally prescribed limits, he will probably arrest you for DUI. When you have been arrested, you may be required to take a post-arrest DUI test at the police station. On the other hand, if you have a low BAC, he will let you go after issuing a warning or traffic ticket.

Post-arrest DUI tests are considered evidentiary. This means that the prosecution can use them in court to prove that you were driving while under the influence. As we asserted earlier, if you refuse to submit to the post-arrest DUI test, you may face severe consequences. For instance, the DMV may suspend your driver’s license for one year.

After the arrest, you may be prompted to choose between a blood test or a breath test. However, in some instances, the investigating officer may require you to take a blood test besides or instead of the breath test if he has a reasonable belief that you are under the influence of drugs.

Law enforcement officers should adhere to Title 17 of the California Code of Regulations when administering these tests. Title 17 enlists strict procedures on how these tests should be taken, including how blood samples should be drawn, how the testing kits should be maintained and calibrated, and how the results should be interpreted, among others. If the police do not observe any of these procedures, your defense attorney can assert that the results were not accurate.

How BAC is Used During DUI Court Cases

In a DUI court case, the prosecution will utilize BAC to prove the defendant’s guilt. BAC will help demonstrate the criminal act of the accused person in two ways. It will show that he/she has exceeded the prescribed legal limits and thus should be held criminally liable for DUI per se. Also, it can demonstrate that the accused person was physically impaired and, therefore, should be convicted of driving under the influence.

For the court to convict you of DUI per se, it will rely on an 'objective' test of the level of intoxication. If the BAC exceeds a certain level, the court will convict the motorist since it is convinced that he/she drove while impaired.

Besides the objective test, the prosecutor can use the 'subjective test' to show the court that you were driving while intoxicated. BAC is one of the elements used in the subjective test – the higher it is, the higher the chances are that the motorist was impaired. Apart from the BAC, the prosecutor will have to rely on other elements to prove the defendant's guilt using the subjective test. Some of these elements include whether the motorist manifested any physical symptoms of intoxication, the motorist's driving pattern, and oral testimonies from eyewitnesses, including the vehicle's passengers.

Breath Tests vs. Blood Tests: Which One Should you choose?

Unfortunately, we cannot provide you a straightforward answer to this question. Both breath and blood tests have their own advantages, and an experienced DUI defense attorney can challenge each of them.  

What you should do after you have been arrested for DUI is to remain calm and polite and to talk less about the incident to the investigating officer. Note that the court cannot convict you of DUI just because you had a high BAC. This is because there are other elements that the prosecution must prove beyond a reasonable doubt. Also, you should remain silent after the arrest because the investigating officer can use what you say as evidence against you.

Typically, most people who are arrested for DUI opt for a breath test. The main pros of breath tests are that they are less stressful and less invasive, and they deliver the results instantly. On the other hand, the major advantages of blood tests are that they are highly accurate, and police officers can't utilize them to frame you for DUI because part of your samples will be saved, and you can choose to test them independently.

Should I Refuse to Take a BAC Test?

The main advantage you will accrue when you refuse to take a BAC test is that you will weaken the prosecutor’s case since he/she will find no sure way to prove that you were driving while under the influence. This way, you may avoid a DUI criminal conviction. However, the prosecution can still prove that you were guilty by showing the court how you exhibited physical symptoms of intoxication and how reckless your driving patterns were.

You may refuse a pre-arrest DUI test without the risk of facing any legal consequences, provided that you are over 21 years, and you are not serving a probation term for a prior DUI conviction. On the other hand, post-arrest DUI tests are compulsory, and when you refuse to take them, the court may assume that you have already admitted guilt. The consequences that you may face when you fail to submit to a post-arrest DUI test include automatic suspension of your driving license for up to one year, and additional jail time and an order to attend a DUI educational program for nine months upon conviction.

Despite the enlisted grievous consequences of failure to submit to the BAC test, it can still be a perfect choice for you if you don't rely entirely on driving to move around because you won't suffer from an automatic suspension of your license. A refusal will also be a good choice if you are very drunk, and you don't want to face the additional penalties of aggravated DUI (having a BAC of 0.15% or higher). We know that extremely drunk motorists may be unable to make the best decision on opting to take the DUI test. Regardless of what you decide at that moment, you should consult a DUI defense attorney to discuss the way forward.

How to Fight DUI Blood/Breath Test Results

Just because the test indicated a high BAC, it does not mean that the testing kit is accurate; or the court will automatically convict you of DUI. Various potential errors can emerge in the blood/breath testing process. When your defense attorney discovers any of these errors, he will use them to challenge the results.

Generally, a DUI defense attorney can challenge a BAC result by adducing the following arguments:

  • The investigating officer didn’t advise the defendant properly of the consequences and choices involved before making him submit to the DUI test
  • The defendant had rising blood alcohol when the test was taken
  • The police officer didn’t observe the correct procedure while administering the test
  • The defendant’s mouth had residual alcohol at the time when the breath test was taken
  • The testing kit was not calibrated accurately
  • The motorist was observing a low-carb, high-protein diet
  • The police officers mishandled the blood or breath sample and probably contaminated it
  • The accused person has a medical condition such as diabetes or GERD that can result in a falsely high BAC reading

Find a DUI Defense Attorney Near Me

You can reach out to us for help if you or your loved one has been charged with the offense of driving under the influence in Van Nuys. We offer free consultations. Call our Van Nuys DUI lawyer today at 818-253-1913 to discuss how you can build an excellent defense strategy, as well as challenge the credibility of the BAC results.