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Understanding DUI Breath Tests in California

Posted by Richard Wagner | Apr 03, 2023

DUI Breath Tests In California 

When you have been pulled over and are suspected of drunk driving, you could be asked to perform a drunk driving breath test. Misconceptions exist about what your rights are and what these types of tests are.

Misunderstandings can lead to more problems, especially if you are facing DUI charges in California.

At The Law Office of Richard Wagner, our DUI defense lawyer in California helps clients understand all aspects of their drunk driving case. Richard Wagner believes informed clients make better decisions about their DUI case. If you have questions or want to speak to discuss your DUI in California, call (714) 721-4423 to schedule a FREE consultation. 

What Are Breathalyzers?

Police officers use breath test devices, commonly called as “breathalyzers,” in roadside testing and following arrests to help determine whether an alleged drunk driver was under the influence of alcohol while operating a vehicle.

There are over 150 models of breathalyzers created by over 25 different firms that have been approved by the National Highway Traffic Safety Administration (NHTSA) for DUI breath testing. 

One of the first breath testing machines was the Drunkometer®

Drunkometer breathalyzer

The two technologies used today to measure alcohol in breath samples are electrochemical (fuel cell) and infrared infrared spectrophotometry.

These tests can be used for drivers of cars and trucks as well as motorcycles, boats, and other vehicles as defined by their respective state.

There are two different times when the police will try to get you to blow into a breathalyzer:

  1. the preliminary alcohol screening test (PAS) before you are arrested -- and
  2. the evidential breathalyzer, after you are arrested.

Confusion arises because both "categories" are frequently referred to as "breath tests."

Preliminary Alcohol Screening (PAS) Tests

A preliminary alcohol screening test or PAS test is a breathalyzer test conducted using a handheld portable breath machine in the field, meaning on the side of the road during a traffic stop or DUI investigation. Unlike other states or jurisdictions, PAS test results are admissible in Southern California courts.

PAS tests are optional if you are age 21 or older, and not on DUI probation. If you are under age 21 or on DUI probation, then you have to take the PAS test. If you refuse the PAS, then you will suffer serious consequences.  

Police give PAS tests when they have believe you have been driving under the influence of alcohol. The police usually try to get you blow into the PAS machine after field sobriety testing. Maybe your speech was slurred or your eyes were red and watery. If you "fail" the PAS test, that could be probable cause to arrest you for a drunk driving offense. A PAS result can also be used together with poor performance on field sobriety tests as probable cause to arrest you.


After an arrest for a drunk driving offense, you will have to take a blood or breath test. Typically, these are referred to as chemical tests.


One of the first Breathalyzer® machines.

The breathalyzer used by the police in Orange County both before and after an arrest are the same - Alco-Sensor V XL by Intoximeters Inc.

The Alco-Sensor V XL uses fuel cell technology. It is a small, lightweight, battery-operated handheld devices.

(Side Note: Intoximeters, Inc. has manufactured over 30 different breathalyzers including the Alco-Sensor III, Alco-Sensor IV, Alco-Sensor IV XL, and Alco-Sensor V).

In Los Angeles, the breathalyzer police use after you are arrested is not a portable machine. It is located at the jail or police station. In LA, they typically use the Datamaster DMT or EC/IR II. 

All breathalyzer machines are subject to calibration requirements established by Title 17 of the California Code of Regulations.

15-Minute Observation Period

Before you blow into a breathalyzer, the officer is required to have you "under continuous observation for fifteen minutes" before providing a breath sample. Title 17 of the California Code Regulations, Section 1221.1.

The purpose of this observation period is make sure you did not put anything in your mouth, or you did not regurgitate, burp, vomit or drink anything. If any of these were to happen, the breath sample could be contaminated and the results could be inflated. 

Do I Have a Right to Refuse a Breath Test in California?

Whether you are in Orange County, Los Angeles or anywhere else in California, you can refuse a breath test in either situation. Preliminary Alcohol Screening tests in the field are typically voluntary if you are 21 and over and not on DUI probation; while tests after you are arrested and breathalyzers at the police station while you are in police custody are not voluntary. You can, however, still refuse either one.

Keep in mind, though, that you should be ready for drastic consequences stemming from the refusal. Consequences include DMV license suspension or revocations.

All states have their own variation of implied consent laws. These laws basically say that you implicitly agree to obey the rules of the road when you get a driver's license. As such, you also implicitly agree to any chemical tests (breath, blood, or urine tests) in exchange for the privilege of operating a vehicle in the state.

If you refuse, the state's DMV can impose an automatic license suspension and fines against you. You do not have to be charged and convicted of a drunk driving offense to have your license suspended or revoked.  Although you are entitled to have a DMV hearing to challenge the legality of the suspension.  

What's more, in some courts, your refusal may be used against you in court as evidence that you knew you were guilty - they refer to it as "consciousness of guilt." If you are convicted, your sentence might include jail time.

Further, if you refuse, the officer will most likely get a search warrant to get your blood sample. Blood tests are much more reliable and accurate.

If you were arrested in Southern California, you should speak to a drunk driving defense lawyer who handles both DMV and criminal DUI cases. For DMV cases, you have the right to a hearing to challenge the automatic license suspension if, for example, the police failed to warn you of the consequences.

The officer must explain the consequences in detail and so that you can understand them. Criminally, you can fight DUI-related charges and be successful.

Common Problems with Breathalyzers in California

Breath tests can be unreliable under certain situations or circumstances.

Problems with breathalyzers can be categorized as those resulting from the testing device or machine, the individual operating the device, or the test sample.

Problems with the Breathalyzer Device

  • Improper calibration
  • Broken or otherwise not maintained properly
  • Not specific for Alcohol
  • Margin of Error
  • RFI /Electromagnetic Interference 

Issues with the Administration of the Test

  • Failure to follow Title 17 
  • Improper instructions 
  • Failure to follow testing manual
  • Testing performed by an untrained person

Causes of Improper Breathalyzer Test Readings

  • Pre-existing conditions or other medical conditions suffered by the test taker
  • Medications, foods, or drinks
  • Mouth alcohol / regurgitation 
  • Certain diets, like Keto
  • False High Readings During the Absorptive State

Breath tests can be challenged. A criminal defense lawyer can file motions to suppress or exclude the results. Sometimes, if successful, this could result in dismissal of the charges or an acquittal.

Five Ways To Beat DUI Breath Tests in California

A breath test is often a substantial part of the prosecution's case involving DUI offenses. For that reason, it is essential to ensure that a breath test was given correctly and the results are accurate.DUI defense attorneys who have been well trained and have experience in these cases can identify a problem with a breath test and take proper action to suppress it as evidence.

At The Law Office of Richard Wagner, we can take any of the following actions, depending on the specific facts and circumstances of your case:

  1. Attack the reliability of the breath test. Many reasons exist why we may not be able to rely on the results of a breath test, like a faulty machine, improper administration, or health issues with the test taker.
  2. Prove the breath device was not properly calibrated. Each state has its own laws on calibration, but there is a difference between calibration check records and records showing a calibration of the breath machine. The first is to check to see if the machine is properly measuring samples. The latter is an actual adjustment or calibration of the machine.  
  3. Prove device was not properly maintained. Typically, the date and time of repairs and maintenance, as well as the nature and extent of and who performed the maintenance and repairs must be logged.
  4. Prove there was a lack of training or an operator's error. Police must be trained in order to conduct breath tests. An untrained or uncertified police officer may not properly administer the test. In some cases, the police officer is trained to use one breath machine, but not to use the one that was used for you. 
  5. Prove records were not properly maintained. Records should be kept to show proper calibration and maintenance, and failure to keep those records updated can be used to prove the device was not properly calibrated or maintained as the law requires.

During the discovery phase of your criminal case, DUI Attorney Richard Wagner will obtain the information and evidence needed to support arguments against the breath test's admissibility.

Contact a DUI Defense Lawyer in California Today

You can have your day in court to challenge DUI charges regardless if you took and "failed" a breath test or refused one. With the right DUI defense lawyer in California, you can be successful. Contact The Law Office of Richard Wagner today by calling us at (714) 721-4423 or filling out an online form to schedule a FREE consultation. We will review your case and discuss your best legal options.

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Richard Wagner

Attorney Profile Defense Lawyer Richard Wagner upholds and defends freedoms and liberties enshrined in our United States and California Constitutions.  “Richard was able to achieve an even better outcome for my case than what we initially thought was possible. I couldn't be more grateful to h...

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