How A Breathalyzer Test Affects A DUI Case

DUI Defense Legal Guide

A DUI breathalyzer test including at what point the test was taken and how many times the test was taken can influence the evidence gathered by prosecutors and ultimately the DUI case itself.

Implied Consent

California’s driving under the influence (DUI) law includes an implied consent law. This law holds that any person who drives a motor vehicle is deemed to have given his or her consent to chemical testing of his or her blood or breath for the purposes of determining the alcoholic content of his or her blood (BAC), if lawfully arrested for a DUI1

In simple terms this basically means that you agree to a breath, blood, or urine test if arrested for DUI

The test will be incidental to a lawful arrest and will be administered at the direction of a police officer having reasonable cause that you were driving under the influence of alcohol or drugs.2 The officer is required to inform the driver that refusal to take a breath or blood test will result in an enhancement of penalties in addition to the standard DUI penalties.3

Requirement Is Post Arrest

It is important to remember that the implied consent law only applies to blood and breath tests requested after a lawful DUI arrest. You may refuse to take a breath test, also known as a preliminary alcohol screen, prior to your actual arrest4.

However, if the officer has reasonable cause to suspect you are driving under the influence based on other evidence such as the field sobriety tests and you are lawfully arrested, you must then submit to a breath test.

Pre-Arrest vs. Post Arrest PAS Test

If the officer suspects that you may be under the influence, then you are likely to be asked to submit to certain field sobriety tests (FST) and/or a PAS, or preliminary alcohol screening test. The PAS is a hand-held device that takes your breath and registers your BAC, similar to a standard breathalyzer.

A major difference between a PAS and the standard breathalyzer is that the PAS is not subject to the same rules regarding training of operators and maintenance requirements to which a standard or more sophisticated breath testing machine must adhere. Consequently, PAS results are not as accurate or reliable.

You are not required to undergo any FST or blow into the PAS if you are at least 21 and not on DUI probation. Should you refuse, your refusal may not be used to suspend your driver’s license or result in enhanced jail time.

Drivers Under 21

There is an exception if you are a motorist under 21 years of age.

As an underage driver, you do not have the option of refusing to take the PAS and, if the PAS indicates your system has any appreciable level of alcohol, the result can be used against you to result in the suspension of your driver’s license for one year.

Underage drivers can be charged under Vehicle Code § 23136 (zero tolerance for underage drivers) and VC § 23140 (driving with a BAC of 0.05% or greater).

Drivers on Probation

If you were previously convicted of DUI, then you were likely placed on probation for at least 3-years. During this time, you may not drive with any measurable amount of alcohol in your system pursuant to CVC § 23154(a), which is a zero tolerance law for drivers on DUI probation.

Under this code section, your BAC may be measured by either the PAS or a DUI chemical test and either may be introduced against you. If you refuse to take the PAS, your driver’s license may be revoked for 1-3 years.

Further, you are in violation of your probation for driving with alcohol in your system. Consequently, you face jail time for violating probation in addition to whatever jail time the court may impose for your new DUI conviction.

Title 17 Breath Testing Requirements

When arrested for DUI, you will be asked to submit to chemical testing to measure your BAC or at least detect the presence of a drug. If you choose to take a PAS test the officers are required to follow title 17 of the California Code of Regulations.

Title 17 Requirements
  • An officer must continuously observe you for at least 15-minutes before the breath test is administered to ensure you do not eat, drink, smoke, vomit, burp, or regurgitate as this can affect the test results
  • Ensure that the breath sample is from deep within the defendant’s lungs and not from the mouth or upper lung area
  • Taking 2 separate breath samples that result in determinations of BAC that do not differ from each other by more than 0.02 grams per 100 milliliters
  • Having the device checked for accuracy and calibrated (if necessary) every 10 days or after 150 uses, whichever is sooner
  • Maintaining records for the instrument to show frequency of determination of accuracy and the identity of the person who performed the determination
  • That records for the maintenance of the instrument be kept at the forensic alcohol laboratory showing compliance with this section
  • That the operator/person responsible for maintenance and calibration of the device shall be a forensic alcohol supervisor, forensic alcohol analyst, forensic alcohol trainee, or person trained under Section 1221.4(a)(3) and who may be called upon to operate a breath-testing instrument in the performance of his or her duties

These regulations apply to post-arrest breath tests and not to pre-arrest testing where the PAS is utilized.

Legal Consequences Of Title 17 Violation

Your defense attorney can move to suppress the breath or blood test results but the courts have ruled that such omissions are not fatal to the prosecution’s case against you. In other words, the failure to adhere to the provisions of Title 17 goes to the weight of the evidence5. Similarly, use of a technician not properly trained in the administration of a blood test will not invalidate the test results6.

Your attorney can argue that an omission tainted the breath, blood or urine sample and the BAC or drug results are inaccurate or unreliable. This should at least create reasonable doubt in the mind(s) of the trier-of-fact.

Difference Between Taking 1 or Mulitple Breath Tests

One defense is that because only one test was taken, that the prosecution cannot prove beyond a reasonable doubt what your BAC was at the time you were driving since the alcohol you consumed had not yet been absorbed by your body.

If only one chemical test is given, it is not possible to determine if your BAC was rising or falling. With 2 tests, then a prosecutor can determine if it was rising or falling since one test will be higher than the other. The first test can be the PAS taken pre-arrest. Its results are evidence that can be used against you. The second test will be the breath or blood test given post-arrest.

For example, you refused the PAS but then the chemical test is administered 30 minutes or more after you were stopped and more than 45 minutes since your last drink. If your BAC was 0.08% when tested, the prosecutor may have trouble establishing beyond a reasonable doubt that this was your BAC or that it was higher when you drove 30 minutes earlier since there was no test result at that time.

Using the principles of alcohol absorption, your BAC could easily have been rising when you were tested and that it was under 0.08% when you were driving.

Multiple Breath Tests

But if you did take the PAS which registered 0.09% and the second or chemical test had a result of 0.08%, then the prosecution could argue your BAC was falling and that it was much higher at the time you did drive.

Title 17 Requirements For Second Sample

Under Title 17, breathalyzer operators for the BAC chemical test, administered post-arrest, are required to take 2 separate breath samples that result in determinations of your BAC that do not differ from each other by more than 0.02 grams per 100 milliliters. The technician can take multiple samples if a second one is not within the 0.02 grams standard to obtain a subsequent sample that is in compliance.

The tests need not be consecutive so that a third or fourth sample may be within 0.02 grams of the initial test.

If the technician failed to take a second sample or submitted samples that were not within the standard, then your attorney can argue that the results are invalid and unreliable7. However, the court is not required to suppress the results.

Explanation of Partition Ratio

The accuracy of the PAS can be challenged based on differing partition ratios in the general public. The PAS device is based on the assumption that 1200 milliliters of a person’s breath contains the same amount of alcohol as 1 milliliter of blood.

Research indicates, however, that partition ratios vary from as much as 900:1 to 2000:1. What this means is that two individuals who may have the same actual BAC of 0.08% could have blown into the PAS and registered different results of 0.07% to 0.12%.

Courts allow the introduction into evidence of testimony showing the potential of falsely elevated readings of the PAS. Along with the rising BAC defense and other exculpatory evidence, your attorney can argue that there is sufficient reasonable doubt to find you not guilty.

If used at a DMV hearing, it is possible your driver’s license might not be revoked in the face of this and other convincing evidence that your BAC was more than likely not 0.08% or more and you were not under the influence.

How a PAS Result Affects a DUI Case

Even though a PAS device does not have to adhere to the same regulations or standards set forth in Title 17 that a breathalyzer must meet, its results are admissible in court that you were under the influence when driving8. However, before the prosecution can use the results of the PAS, he or she must first show:

  • Compliance with Title 17; or,
  • Foundational elements of a properly administered test and,
  • A qualified operator
Under 21 Years Old

If you are under 21 or on DUI probation, your refusal to take the PAS will result in your arrest even if you subsequently take the chemical test and your results are under 0.08%. Your arrest is based on the fact that you were either drinking underage or that you violated a condition of your probation that you not drink at all, regardless of your BAC result.

Over 21

If you are at least 21 years of age and not on DUI probation, you can legally refuse to take the PAS without any consequences. As indicated, the officer can still arrest you for DUI based on other evidence and then ask that you submit to chemical testing.

If you do take the PAS and its results are 0.08% or more, you will be placed under arrest for DUI and then asked to take the chemical test. But if the chemical test (breathalyzer or blood test) is under 0.08%, you will likely not be charged with driving with a BAC of 0.08% or more per VC 23152(b), though you could still be charged as being under the influence pursuant to VC § 23152(a).

If not charged, you could still face other violations that prompted your stop, such as unsafe lane change, reckless driving, speeding, or others.

If you do go to trial, the prosecution can introduce the results of your PAS test as evidence that you were driving impaired. This can be used in conjunction with your chemical test results.

As indicated earlier, if the second test result is higher than the PAS result, your attorney can argue that your BAC was still on the rise and that it is highly probable that your BAC was under 0.08% when you were driving. This is one way of rebutting the presumption that you were driving while impaired.

Breath Testing FAQs

If I believe I was unlawfully arrested, should I refuse to take a chemical test?

If you are placed under arrest, whether you believe it was lawful or not, failure to submit to the implied consent law related test will result in more severe consequences. It is usually easier for your attorney to get the results of an unlawful breath test thrown out by arguing that the arrest was unlawful than it is for your attorney to argue that you refused the breath or blood test based on your assumption that the arrest was unlawful.

What if I have a medical condition that prevents me from taking a breath test?

Having a low lung capacity or a medical disorder that prevents you from submitting to a breath test does not excuse you from taking a chemical test altogether. The officer may take a blood test if you cannot take a breath one.

Is an officer allowed to require me to take a blood test instead of a breath test?

If the officer suspects that you are driving under the influence of drugs or both alcohol and drugs and places you under arrest, he can then require you to take a blood test. Only a blood test will show whether or not you have been driving under the influence of drugs.

Next Steps

If you have been arrested and would like to learn more about what attorneys charge.

If you want to understand why its important to have an attorney represent you.

If you are ready to discuss a pending case contact the Aizman Law Firm at 818-351-9555 for a free confidential consultation.


  1. California Vehicle Code 23162(a)(1)(A.) -A person who drives a motor vehicle is deemed to have given his or her consent to chemical testing of his or her blood or breath for the purpose of determining the alcoholic content of his or her blood, if lawfully arrested for an offense allegedly committed in violation of Section 23140, 23152, or 23153. If a blood or breath test, or both, are unavailable, then paragraph (2) of subdivision (d) applies., available at []
  2. California Vehicle Code §23162(a)(1)(c) – The testing shall be incidental to a lawful arrest and administered at the direction of a peace officer having reasonable cause to believe the person was driving a motor vehicle in violation of Section 23140, 23152, or 23153., available at []
  3. California Vehicle Codet §23162(a)(1)(D) – The person shall be told that his or her failure to submit to, or the failure to complete, the required chemical testing will result in a fine, mandatory imprisonment if the person is convicted of a violation of Section 23152 or 23153, and (i) the suspension of the person’s privilege to operate a motor vehicle for a period of one year, (ii) the revocation of the person’s privilege to operate a motor vehicle for a period of two years if the refusal occurs within 10 years of a separate violation of Section 23103 as specified in Section 23103.5, or of Section 23140, 23152, or 23153 of this code, or of Section 191.5 or subdivision., available at []
  4. California Vehicle Code 13353.1., available at []
  5. People v. Adams (1976) 59 Cal.App.3d 559; People v. Bury (1996) 41 Cal.App.4th 1194 []
  6. People v. Esayian (2003) 112 Cal.App. 4th 1031, 1039 []
  7. People v. Adams (1976) 59 Cal.App.3d 559, 567 []
  8. People v. Williams (2002) 28 Cal.App.4th 408, 417 []

Leave a reply

Related Posts