DUI Laws
Blood Tests in California DUI Cases — Procedures, Accuracy, and How to Challenge Them
A blood test is often considered the most accurate measure of BAC in a DUI case — but the results can be challenged on chain of custody, lab procedures, fermentation, and Title 17 compliance. Learn how Attorney Michael P. Kade attacks blood test evidence.
By Michael P. Kade — Former LAPD Officer & Criminal Defense Attorney · Updated
Educational purposes only — not legal advice. This article provides general information about California DUI law and does not create an attorney-client relationship. Consult a licensed attorney for advice specific to your situation.
Key Takeaways
- —Blood tests must follow Title 17 of the California Code of Regulations to be admissible
- —You have the right to request an independent analysis of your blood sample (a 'blood split')
- —Fermentation of the blood sample can artificially inflate the BAC reading
- —Chain of custody errors can render a blood sample inadmissible
- —Rising blood alcohol defense argues BAC was below 0.08% while driving even if higher at the time of the test
When you are arrested for DUI in California and choose a blood test — or when an officer obtains a warrant for your blood — the sample becomes a critical piece of evidence. Unlike breath tests, blood samples can be preserved and independently retested. That cuts both ways: the prosecution has a more durable piece of evidence, but the defense has the opportunity to scrutinize every step of the collection, storage, and analysis process.
Title 17 Requirements for Blood Collection
California Code of Regulations, Title 17, §§ 1219–1221 set out strict requirements for how blood samples must be collected, stored, and analyzed in DUI cases. The phlebotomist must use a non-alcoholic antiseptic to clean the draw site. The sample must be placed in a tube containing the correct ratio of anticoagulant and preservative. The tube must be properly labeled, refrigerated, and maintained in a secure chain of custody. Any deviation from these requirements is grounds to challenge the admissibility or weight of the test result.
The Blood Split — Your Right to Independent Testing
Under California Vehicle Code § 23158, you have the right to have a portion of your blood sample independently tested by a laboratory of your choosing at your own expense. This is called a 'blood split.' Your attorney should request the blood split as soon as possible after arrest, because samples can degrade over time. An independent analysis may reveal a lower BAC than the prosecution's lab found, or may identify procedural errors in the original testing.
Fermentation and Contamination
If a blood sample is not properly preserved — for example, if the preservative sodium fluoride is absent or insufficient — the blood can ferment after collection, producing alcohol that was not present in the driver's body at the time of the draw. This phenomenon, sometimes called in vitro ethanol production, can artificially inflate the BAC reading. Defense experts can test the sample for signs of fermentation and present that evidence to the jury.
Rising Blood Alcohol Defense
Alcohol is absorbed into the bloodstream over time. If you had your last drink shortly before driving, your BAC may have been rising during the drive and may have been below 0.08% while you were actually behind the wheel — even if it tested above 0.08% when the blood was drawn 30 minutes to an hour later. A forensic toxicologist can calculate a retrograde extrapolation to estimate your BAC at the time of driving, which may support a not-guilty verdict on the per se charge under Vehicle Code § 23152(b).
Penalties at a Glance
| Offense / Situation | Potential Penalty |
|---|---|
| BAC 0.08%–0.14% — first offense | Standard DUI penalties apply |
| BAC 0.15%+ — first offense | Enhanced penalties; longer DUI school; IID required |
| BAC 0.16%+ — first offense | Potential aggravated DUI treatment in sentencing |
Penalties shown are general ranges. Actual sentences depend on the specific facts of your case.
How Attorney Kade Defends These Cases
- —Request a blood split immediately and have the sample independently analyzed
- —Obtain and review the lab's chain of custody documentation for every transfer of the sample
- —Hire a forensic toxicologist to evaluate the sample for fermentation or contamination
- —Challenge Title 17 compliance in the collection, storage, and analysis process
- —Present a rising blood alcohol defense through retrograde extrapolation
- —Subpoena the lab analyst and cross-examine them on their methodology and training
- —Challenge the qualifications of the phlebotomist who drew the blood
Frequently Asked Questions
While you are not legally required to have an attorney, a DUI conviction carries serious consequences — fines, license suspension, possible jail time, and a permanent criminal record. An experienced DUI attorney can challenge the evidence, negotiate with prosecutors, fight your DMV hearing, and potentially get charges reduced or dismissed. The cost of an attorney is almost always less than the long-term cost of a DUI conviction.
A California DUI case typically takes 3 to 12 months to resolve, depending on the county, the complexity of the case, and whether it goes to trial. Misdemeanor DUI cases in Los Angeles County often take 4 to 8 months. Felony DUI cases take longer. Your attorney can give you a more specific estimate based on the facts of your case and the court's current caseload.
After a DUI arrest: (1) Do not make any statements to police beyond identifying yourself. (2) Contact a DUI attorney as soon as possible — ideally within 24 hours. (3) Call the DMV Driver Safety Office within 10 days to request an APS hearing or your license will be automatically suspended. (4) Write down everything you remember about the stop, the tests, and the arrest while it is fresh.