Orange County DUI Lawyer Blog
A DUI arrest in California does not automatically mean a conviction. One of the most powerful — and frequently successful — defense strategies is challenging the validity of the breath test. Breath testing technology, while widely accepted, is riddled with potential errors that an experienced DUI defense attorney can exploit. Understanding these vulnerabilities is critical for anyone facing charges under California Vehicle Code Sections 23152 or 23153.
How Breath Tests Work — and Where They Fail
California law enforcement primarily uses two devices: the Draeger Alcotest and the Intoxilyzer 8000. Both rely on infrared spectroscopy to estimate blood alcohol concentration (BAC) from a breath sample. The device measures ethanol molecules in deep lung air (alveolar air) and extrapolates a BAC using a partition ratio — the assumed ratio of alcohol in blood to alcohol in breath. California courts use a standardized partition ratio of 2,100:1, meaning 2,100 milliliters of breath contains the same alcohol as 1 milliliter of blood. The problem? This ratio varies significantly from person to person and even within the same individual depending on body temperature, lung capacity, and other physiological factors. A person with a higher-than-average partition ratio may produce a falsely elevated BAC reading.
Mouth Alcohol Contamination
Breath machines are designed to measure deep lung air, not residual alcohol in the mouth. However, if a subject has recently belched, burped, vomited, or regurgitated — even partially — alcohol from the stomach can be introduced into the mouth, causing the device to register a falsely high BAC. California’s Title 17 regulations require officers to observe the suspect for a continuous 15-minute period before administering the test, specifically to guard against mouth alcohol contamination. If the arresting officer failed to maintain this uninterrupted observation period, the results may be challenged. Any gap in observation — even briefly looking away, completing paperwork, or speaking on the radio — can be grounds for suppression of the test.
Failure to Follow Title 17 Regulations
California Code of Regulations, Title 17, sets the mandatory protocols for collecting, preserving, and analyzing DUI chemical evidence. These rules are not mere suggestions — they are legal prerequisites for the admissibility of breath test results. Violations include failure to administer two separate breath samples within 0.02 g/210L of each other (required for a valid result), failure to properly calibrate and maintain the testing device, use of an instrument that has not been approved by the California Department of Public Health (CDPH), and failure to document the observation period. Any deviation from Title 17 procedures gives the defense a strong basis to argue that the results are scientifically unreliable and should be excluded from evidence.
Instrument Calibration and Maintenance Records
Breathalyzer machines must be regularly calibrated using reference samples of known alcohol concentration. Defense attorneys routinely subpoena the complete maintenance and calibration logs for the specific device used in the arrest. A device that was out of calibration, overdue for service, or had a history of malfunctions at the time of the test provides powerful ammunition for the defense. California law requires these records to be preserved, and prosecutors must disclose them. Gaps in maintenance history, failed calibration checks, or repairs made shortly before or after an arrest can all cast serious doubt on the accuracy of the reading.
Medical and Physiological Conditions
Certain medical conditions can produce falsely elevated breath test readings. The most significant is auto-brewery syndrome, a rare condition where the body ferments carbohydrates into alcohol internally. More commonly, gastroesophageal reflux disease (GERD), acid reflux, and hiatal hernias can cause stomach gases — including alcohol vapors — to rise into the esophagus and mouth during the testing period, contaminating the sample. Diabetics and individuals on high-protein or low-carbohydrate diets may produce acetone through ketosis, and older breath test machines sometimes misidentified acetone as ethyl alcohol, generating a false positive reading. High body temperature (fever) also causes breath alcohol readings to rise, as the device does not account for variations in body temperature above the assumed 34°C.
Rising Blood Alcohol Defense
California law requires the prosecution to prove that a defendant’s BAC was 0.08% or higher at the time of driving — not merely at the time of testing. Alcohol absorption is a dynamic process. If a person consumed alcohol shortly before driving, their BAC may have been below the legal limit while operating the vehicle but continued to rise by the time they were tested 30, 45, or even 90 minutes later. This ‘rising BAC’ defense is supported by toxicological expert testimony and can create reasonable doubt about the defendant’s actual BAC while behind the wheel.
Where DUI Cases Arise: Major Cities in Los Angeles and Orange Counties
DUI arrests occur across both counties in virtually every city. Major cities in Los Angeles County where DUI cases regularly appear in court include:
Los Angeles, Long Beach, Glendale, Santa Monica, Pasadena, Torrance, Burbank, Inglewood, West Covina, Downey, Costa Mesa (LA border area), El Monte, Pomona, Compton, Carson, Hawthorne, Alhambra, Whittier, Norwalk, Gardena, Lakewood, Paramount, Bellflower, Lynwood, Culver City, El Segundo, Manhattan Beach, Redondo Beach, Hermosa Beach, Malibu, Calabasas, Chatsworth, Reseda, Van Nuys, North Hollywood, Studio City, Sherman Oaks, Encino, Tarzana, Woodland Hills, Thousand Oaks (nearby), Lancaster, Palmdale, Monrovia, Arcadia, Temple City, San Gabriel, Monterey Park, Montebello, Pico Rivera, Bell, Bell Gardens, Huntington Park, South Gate, Lynwood, Maywood, and Vernon.
Major cities in Orange County where DUI cases frequently arise include:
Anaheim, Santa Ana, Irvine, Huntington Beach, Garden Grove, Fullerton, Orange, Costa Mesa, Mission Viejo, Westminster, Newport Beach, Buena Park, Lake Forest, Tustin, Fountain Valley, Yorba Linda, San Clemente, Laguna Niguel, Brea, La Habra, Stanton, Cypress, Los Alamitos, Seal Beach, Dana Point, San Juan Capistrano, Laguna Beach, Laguna Hills, Rancho Santa Margarita, Aliso Viejo, and Placentia.
The Bottom Line
A breath test reading above 0.08% is not the end of a DUI case — it is the beginning of a legal battle. Skilled defense attorneys in Southern California understand that these machines are imperfect instruments operated by fallible officers under strict procedural requirements. By scrutinizing the device’s calibration records, the officer’s conduct during the observation period, the defendant’s medical history, and the timing of alcohol consumption relative to driving, a defense attorney can often raise sufficient reasonable doubt to secure a reduction in charges or an outright dismissal. Anyone charged with a DUI in Los Angeles or Orange County should consult with an experienced DUI defense lawyer before making any decisions about their case.Call William Weinberg at 949.474.8008 or reach him at bill@williamweinberg.com