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Understanding DUI/DWI Arrests and Breath Tests in California

When you have been pulled over and are suspected of drunk driving, you could be asked to provide a breath sample. 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/DWI charges in California.

At Compass Legal Group, APC, our DUI/DWI defense lawyer in Los Angeles, Ventura, and Santa Barbara Counties helps clients understand all aspects of their drunk driving case. We believe informed clients make better decisions about their DUI/DWI case. If you have questions or want to speak to a criminal defense lawyer in California, call us at (805) 852-5141 to schedule a Free 30-minute Consultation.

What Are Breath Tests?

Police officers use breath tests in roadside testing and following arrests to help determine whether an alleged drunk driver was under the influence of alcohol while operating a vehicle. These tests can be used for operators of cars and trucks as well as operators of motorcycles, boats, and other vehicles as defined by their respective states.

There are two types of breath tests: the preliminary breath test (PBT) (also known as preliminary alcohol screenings) and the breathalyzer. Both "types" are often simply called "breath tests," and that's where the confusion comes in. By referring to both as breath tests, people assume they are the same thing but they are not. Each is administered for different reasons and purposes.

Preliminary Breath Tests

A preliminary breath test or alcohol screening is a breath alcohol test conducted using a portable breath machine in the field, meaning on the side of the road during a traffic stop or DUI/DWI investigation. The PBT measures a person's breath alcohol content (BrAC). Portable breath test results are almost always inadmissible in court because they are unreliable. However, you would want to speak to a drunk driving attorney to make sure what your specific state law says about PBT results and admissibility.

PBTs are administered when a police officer has reasonable grounds to believe you are unlawfully intoxicated. Maybe your speech was slurred, or your eyes were bloodshot, so the officer asked you to take a breath sample. If you fail the PBT, that could be enough probable cause to arrest you for a drunk driving offense. A PBT result can also be used in conjunction with a failed field sobriety test as sufficient probable cause to arrest you.


After an arrest for a drunk driving offense, you will have to take another test. Typically, this is a chemical test using a breathalyzer. The breathalyzer is not a portable machine and produces more accurate results and can be admitted into court as evidence against you. Approved breathalyzer machines are subject to calibration requirements established by state or federal law.

Before you provide a breath sample via a breathalyzer, the officer should have read the Miranda warning to you. Miranda warnings advise you of your rights. If this warning was not provided to you prior to a breathalyzer test, your constitutional rights might have been violated.

Do I Have a Right to Refuse a Breath Test in Los Angeles, Ventura, and Santa Barbara Counties?

Whether you are in Los Angeles, Ventura, and Santa Barbara Counties or anywhere else in California, you can refuse a breath test in either situation. Breath tests using portable machines in the field are typically voluntary, while tests used at the police station while in police custody are not voluntary. You can, however, still refuse either one.

Keep in mind, though, that you should be ready for consequences stemming from the refusal. Immediate consequences include administrative penalties, while long-term consequences are those that may result in a criminal conviction.

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 agency for motor vehicles 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 -- you just need to refuse a breath test.

In some jurisdictions, your refusal may be used against you in court as evidence that you were drunk driving. If you are convicted, your sentence could include jail time.

Further, if you refuse, the officer may request a warrant to obtain a blood sample. Blood tests are much more reliable and accurate.

If you were arrested in Los Angeles, Ventura, and Santa Barbara Counties, you should speak to a drunk driving defense lawyer who handles both administrative and criminal DUI/DWI cases. Administratively, you can appeal an automatic license suspension if, for example, the police failed to warn you of the consequences. Criminally, you can fight DUI/DWI-related charges and be successful.

Common Problems with the Breath Tests in California

Breath tests using portable machines are known to be unreliable, and that's why they are typically not admissible in court. Breath tests using breathalyzers at the police station, however, are admissible. They can also be unreliable and become inadmissible 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
  • Incorrect chemical solutions
  • Inappropriate modification
  • Faulty programming
  • Broken or otherwise not maintained properly

Issues with the Administration of the Test

  • Failure to read Miranda Warnings
  • Improper instructions or methodology
  • Failure to follow testing protocols
  • 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
  • Residual alcohol from the test taker's mouth
  • Certain diets, like Keto

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 the dismissal of the charges or an acquittal.

Five Ways We Challenge DUI/DWI Breath Tests in Los Angeles, Ventura, and Santa Barbara Counties

A breath test is often a substantial part of the prosecution's case involving DUI/DWI offenses. Therefore, it is essential to ensure that a breath test is performed correctly and the results are accurate. DUI/DWI 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 Compass Legal Group, APC, 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 respective laws on calibration, but it usually involves a certified forensic analyst and verification of the machine's accuracy.
  3. Prove device was not properly maintained. Typically, the date and time of repairs and maintenance and 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.
  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, we will obtain the information and evidence we need to support arguments against the breath test's admissibility.

Contact a DUI/DWI Defense Lawyer in Los Angeles, Ventura, and Santa Barbara Counties Today

You can have your day in court to challenge DUI/DWI charges regardless if you took and failed a breath test or refused one. With the right DUI/DWI defense lawyer in Los Angeles, Ventura, and Santa Barbara Counties, you can be successful. Contact Compass Legal Group, APC today by calling us at (805) 852-5141 or filling out an online form to schedule a Free 30-minute Consultation. We will review your case and discuss your best legal options.

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Compass Legal Group is committed to you. We understand the stress you're shouldering, and strive to make the process as simple and affordable as possible. We offer free consultations to discuss your case, at your convenience. Contact us today to schedule an appointment.