Is Rising Blood Alcohol a Valid Defense for California DUI?

 Posted on October 09, 2025 in DUI

A BAC reading that is at or above the legal limit does not always reflect an individual’s level of impairment while behind the wheel. In the state of California, DUI (California Vehicle Code Section 23152) charges are often based on chemical test results taken after an arrest, even though alcohol levels in the bloodstream continue to rise after a driver has stopped drinking.

This is known as "rising blood alcohol" and can be a defense to DUI charges in some instances. Essentially, the rising blood alcohol defense says that your BAC was below the legal limit (0.08 percent) while you were driving, even though the BAC test later showed a higher level.

Since alcohol is not instantly absorbed into the bloodstream, a defense attorney would need to prove – through expert witnesses and a detailed analysis of the timeline – that your body was still absorbing alcohol while you were driving. This would render the BAC test later inaccurate. A skilled Sonoma, CA DUI attorney can help you understand how the rising blood alcohol defense works and whether it applies in your case.  

Understanding Rising Blood Alcohol

An individual’s BAC continues to rise for 30-90 minutes after his or her last drink. The variables that affect how quickly alcohol is absorbed in the bloodstream include gender, metabolism, whether food was eaten before drinking, and body weight. So, if a person had a couple of drinks right before driving and was stopped shortly thereafter, his or her BAC would continue to rise for another half hour to an hour and a half. This means that the individual may not have actually been impaired at the time he or she was driving.

By the time the police officer does field sobriety tests and transports the individual to the police station, the alcohol has had time to be absorbed, and the BAC is higher. Since prosecution in a DUI case in California relies heavily on breath or blood test results, a defense attorney must challenge the assumption that the BAC at the time of the test was the same as the BAC while the individual was driving.

Penalties for a First-Time DUI in California

A first-time DUI in California is a misdemeanor offense, punishable by 3-5 years of probation, fines between $390 and $1,000 plus court fees, mandatory DUI school, a six-month driver’s license suspension, and the potential for up to six months in jail.

Penalties can increase if there are aggravating factors, such as having a minor in the car, refusing a chemical test, or a particularly high BAC reading. Community service may be ordered, and higher car insurance rates will be in place for several years following a DUI. In some instances, the driver may be required to install an Ignition Interlock Device on his or her vehicle.  

Rising Blood Alcohol Defense and Other Defenses Commonly Used for DUI Charges

If the defense attorney believes rising blood alcohol is a valid defense, he or she may highlight any inconsistencies between the officer’s observations and the chemical test results. The reliability of test timing can also be challenged, with the argument being that the driver’s BAC was below the legal limit while he or she was actually driving. Other defenses that may be applicable include:

• The breathalyzer machine was improperly calibrated.
• The police officer was not sufficiently trained in administering the breathalyzer test.
• The officer had no probable cause for the initial traffic stop.
• The defendant has a medical condition, such as diabetes, that skewed the breathalyzer test.
• The defendant is taking certain prescription medications that affect the accuracy of the test.
• The defendant is on a strict Keto diet, or his or her work involves paint solvents.
• The defendant’s constitutional rights were violated during the arrest and interrogation.

Contact a San Francisco, CA DUI Attorney

A DUI arrest in California does not automatically mean a conviction, especially if your Sonoma, CA DUI lawyer from Burglin Law Offices, P.C. can prove that the rising blood alcohol defense applies in your case.

Defending your charges may require expert witnesses and skilled cross-examination. Attorney Burglin has represented more than 5,000 individuals charged with DUI and has been lead counsel in more than 120 DUI jury trials throughout his 32-year career. To schedule your free consultation, call 415-729-7300.