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Breath Tests

Police DUI breath machine

After a driver has been placed under arrest for DUI, the driver will be informed that per California’s implied consent law, the driver must submit to a breath or blood test.  In this article we will examine the breath test.

What is implied consent?

California’s implied consent law requires that any driver, whether a resident or non-resident, who has been arrested for DUI, submit to a chemical test, either a breath or blood test, to determine the driver’s level of alcohol concentration.


If a person refuses the chemical test, the driver will face increased DUI penalties as well as a mandatory driver’s license suspension regardless of the outcome of the case, including if the case is dismissed.  If you are found guilty, you may be subject to additional time in custody.

What is Title 17?

California’s Title 17 of the Code of Regulations governs the procedures and testing method for both blood and breath tests. Regarding breath test, Title 17 requires a strict protocol be followed when both maintaining and administering breath test.

In order to comply with Title 17, the breath machine must be in good working order,  be calibrated every 10 days or 150 uses, and the user must be trained on the operation of the machine.


Prior to administering the breath test, the user is required to observe the driver for a continuous 15-minute period to see whether the driver smokes, eats, drinks, burps, vomits, or regurgitates anything. 


Title 17 requires that the air for the test be alveolar air, also known as deep lung air.  The user must also administer the test twice and the test results may not differ more than .02.


Failure to follow these procedures closely can create false readings for a driver’s BAC.  However, the courts have ruled that even if these procedures are not followed correctly, this does not exclude the prosecution from using the evidence but goes to the “weight” of it.  In other words, even if a faulty machine or operator administers the test, the prosecution can argue the validity of the results while the defense may ask the jury to disregard them.  A skilled defense attorney knows how to develop such an argument and guide the jury to why they should disregard such evidence in evaluating a case.

What factors can affect a breath test?

There are a variety of factors and medical conditions that can affect the results of a breath test. One of the biggest factors is the presence of “mouth alcohol”.  Mouth alcohol is the term used when residual alcohol remains inside the persons mouth, either in the mucus linings or within the gums.  This usually results from the driver having recently consumed alcohol before the test.  Mouth alcohol typically remains in the mouth for up to 20 minutes, which is why the officer is required to observe the driver for a minimum of 15 minutes to ensure that they did not consume anything.  However, if mouth alcohol is present, it may distort the results.  Typically, a criminalist will testify that the machine used has a “slope” detector that is designed to detect the presence of mouth alcohol and alert the user. While true, if the machine has not been properly calibrated or maintained, then there are instances where mouth alcohol escapes into the testing chamber.


Other issues that can affect the BAC results from a breath test have to do with the general rising blood defense.  After drinking, a driver’s BAC will continue to rise for up to an hour after consuming alcohol. If the test is administered in that period, then the test may produce falsely high numbers based upon the BAC at the time the test was given, not at the time the person was driving.

Dedicated DUI Attorney

Kevin Ballard is a dedicated DUI attorney based in Fairfield who understands how to effectively defend those charged with DUIs. Kevin is one of the few attorneys who is both a former prosecutor and trained as a police officer. As such, Kevin knows first hand how DUIs are handled from the initial traffic stop through prosecution and appeal. Let the Law Office of Kevin L. Ballard help you today defend your rights and protect your liberty.

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