If you are facing a California DUI case, you need an attorney who understands how breathalyzers work. When the police arrest someone for driving under the influence (DUI) in California, the driver has the choice of either a breath test or blood test to determine the amount of alcohol in their system. Breath tests are commonly called breathalyzers. Criminal Defense Heroes, P.C. founding attorney Don Hammond recently attended a focused breathalyzer training, facilitated by the National College for DUI Defense.
Don previously attended an intensive blood testing program called Serious Science for Serious Lawyers, where he spent time in a lab, processing human blood sample for alcohol. He learned how chromatographs work, how to read chromatograms, and where the human errors are in the scientific process. He has used this experience to get great results in several complicated DUI cases. Now, Don has also taken advanced training in breath testing.
At the DUI breathalyzer training, Don learned more about how various types of breath testing devices work. Different California police agencies use different types of machines for DUI breath testing. There are infrared breathalyzers and fuel cell breath testing instruments. Don learned about the differences, and the limitations of each type of device. He got to blow into four different models of DUI breath testing machines, noting the differences in how they operate. Expert toxicologists explained the intricacies of the machines, their flaws, and scientific limitations.
Here’s a video of Don blowing into one machine:
DUI Breath Test Errors
Some errors in DUI breath testing include physiological errors, including alcohol from the stomach mixing with air from the lungs. Some medical conditions, such as GERD or acid reflux can cause this. Other physiology-based errors relate to the temperature of the breath.
Other errors relate to inherent issues with DUI breath testing devices. One of these is the margin of error that applies to any scientific test. Another is that fuel cells degrade over time, leading to less accurate results. The machine also makes assumptions about the ratio of alcohol in the blood to that in the breath. This key assumption is incorrect as applied to most people.
Taking all of the errors into account, a DUI breath test can have over 40% variability. So a breath test result of .12% BAC could actually be as low as .072% BAC. All of this is assuming that the machine is working properly and that the police officer operated it correctly. Given that the legal limit for driving in California is .08% BAC, many drivers who are facing DUI charges are actually innocent. A breath test result of .12% BAC would indicate that the driver was 1.5 times the legal limit, but it may be incorrect.
Here’s Don blowing into another DUI breath testing device:
If you are facing a California DUI charge, you need an attorney with the experience and training to fight the case. Don Hammond has the training and experience to challenge both blood and breath tests. He also has experience fighting the DMV at all levels up to the California court of appeals.
If you are looking for an attorney to fight a California DUI case, you need Don Hammond. He was recognized in 2025 with a Trial Advocacy Award by the National College for DUI Defense. Don has extensive training in DUI breath and blood testing. He has won DUI trials and DMV hearings. He has sued the DMV in court and won, overturning DMV hearing officers who unlawfully suspend our clients’ driving privileges. If you are facing a California DUI case, contact us today at 323-529-3660 for a consultation.
