California DUI Blood Testing
How to Challenge Blood Test Results in Your DUI Case

If you are arrested for DUI in California, you will generally be required to take either a DUI blood test or a DUI breath test. If you refuse, you may face penalties for chemical test refusal.1

If you are charged with California DUI, the evidence against you may include a DUI blood test. But even blood samples are subject to error. These errors can be the basis of a successful defense against the DUI charges.

Mistakes that can make blood tests unreliable indicators of blood alcohol content ("BAC") include:

  • Contamination of the blood after it is collected,
  • Switched or intermingled blood samples, and
  • Fermentation that causes the blood sample to produce its own alcohol inside the vial.

In addition, Title 17 of the California Code of Regulations sets forth detailed protocols for the administration of DUI blood tests.2 If these protocols are violated, you and your DUI defense attorney can challenge the results of the blood test.

The blood sample at the right shows signs of "hemolysis"--a phenomenon that can taint a DUI blood test sample.

Below, our California DUI defense attorneys answer the following frequently asked questions about DUI blood testing in California:

If, after reading this article, you have additional questions, we invite you to contact us at Shouse Law Group.

1. What is Title 17 and How Does It Relate to DUI Blood Tests?

California DUI laws impose strict protocols to ensure the accuracy of DUI blood test results. These rules and regulations are set forth in Title 17 of the California Code of Regulations.3

The requirements of a legitimate DUI blood test under Title 17 include:

  • having a trained technician draw the blood in a hospital environment using accepted medical practices;4
  • sterilizing the draw site with something other than an alcohol based product, to avoid adding external alcohol to the DUI blood sample;5
  • ensuring adequate levels of anticoagulants and preservatives in the vial to prevent contamination or clotting of the sample;6
  • properly storing the blood sample;7
  • using only approved, calibrated instruments to measure BAC;8 and
  • accounting for everyone who had access to the sample to ensure that the chain of custody is recorded and undisturbed.9

If these protocols are not strictly adhered to, accuracy of the DUI blood test may be compromised--and you can challenge the admission of the blood test results as evidence in your DUI case.

Title 17 imposes strict protocols to ensure the accuracy of DUI blood tests.

However, under California law, there is a presumption that blood-alcohol test results have been obtained in compliance with Title 17 regulations. As a result, the burden is on you and your California DUI defense attorney to establish that there was a flaw in the DUI blood testing.10 

The two main strategies that a DUI defense attorney would take to challenge flawed DUI blood test results are:

  • file a motion to have the evidence of the blood sample thrown out of court, or
  • aggressively attack the validity of the blood test BAC results at trial in an effort to get a "not guilty" verdict.

2. Can I Be Forced to Take a Blood Test After Being Arrested for DUI?

DUI blood tests without a warrant

Traditionally, under California's "implied consent law," you have been required to take a DUI blood or breath test if you are arrested for DUI in California--even if the officers don't have a search warrant calling for such a test.11 If you refuse to take either, then you face the following penalties:

  1. suspension of your driver's license for at least one year, and
  2. a mandatory jail enhancement of 48 hours if you are ultimately convicted of DUI.12

But in 2016, the Supreme Court of the United States issued a decision called Birchfield v. North DakotaBirchfield held that it is unconstitutional for a state to make it a crime to refuse a blood test without a lawful warrant. (Requiring breath tests without a warrant is still okay.)13 

The Birchfield case dealt with states that make it a separate crime to refuse a DUI blood test after arrest. California, in contrast, just imposes additional penalties on DUI defendants for blood test refusals. So it remains for California courts to decide if this is also unconstitutional--and thus whether California can no longer penalize you for refusing a DUI blood (as opposed to breath) test without a warrant.

DUI blood tests with a warrant / forced blood draws

If you have been involved in an accident, the arresting officer may seek a warrant for a forced blood draw. This means that the officer has more than the threat of criminal penalties at his/her disposal--s/he can actually physically force you to submit to a DUI blood test.

California law enforcement officials may conduct a forced blood draw for DUI blood testing if they have a warrant.

In this situation, you will be taken to a nearby hospital or medical facility. As many officers as it takes will restrain you so that a lab technician or trained officer can forcefully draw your blood. You may also be subject to a forced blood draw if you are unconscious.

If you are the victim of a forced blood draw, your attorney will be extra vigilant when investigating the procedures that were used to collect your DUI blood sample.

As well-known Barstow DUI defense attorney Michael Scafiddi14 explains:

"It's very likely that a rushed or otherwise unexpected blood draw could involve bad protocol--mistakes that could ultimately vindicate my wrongfully accused client."

3. Can I Re-Do My DUI Blood Test in an Independent Laboratory?

DUI blood testing has one major advantage over a breath test.

A "DUI blood split motion" will enable your DUI defense attorney to independently re-test the blood sample you provided for your DUI blood test.

When you submit to a DUI breath test, the results are instant, and no portion of the sample is saved.15

With a DUI blood test, however, you have the right to have the sample preserved for future re-testing. The arresting officer must inform you of this right at the time of your DUI blood test.16

If you exercised this right, your DUI defense attorney can have your blood sample independently and confidentially analyzed by a private laboratory. This is known in California DUI cases as a “blood split motion.”17

Blood splits allow independent laboratories to evaluate blood samples. An independent lab might conclude that a DUI blood test result showing a BAC of over 0.08% was the result of fermentation or contamination of the sample caused by (among other things):

  • inadequate amounts of preservative in the blood vial,
  • improper refrigeration, or
  • mishandling of the blood vial.

This can make for a very convincing case that you are not guilty of DUI in spite of incriminating DUI blood test results, especially when coupled with other DUI defenses such as the rising blood alcohol DUI defense or lack of probable cause for a DUI traffic stop.

Call us for help…


If you or a loved one would like to learn more about DUI blood testing in California, we invite you to contact us at Shouse Law Group. We can provide a free consultation in office or by phone. We have local offices in Los Angeles, the San Fernando Valley, Pasadena, Long Beach, Orange County, Ventura, San Bernardino, Rancho Cucamonga, Riverside, San Diego, Sacramento, Oakland, San Francisco, San Jose and throughout California.

Additionally, our Las Vegas Nevada DUI defense attorneys represent clients accused of DUI offenses in Nevada. For more information, please see our article DUI blood tests in Nevada.

Legal References:

  1.  Vehicle Code 23612(a)(1)(A) VC – Implied consent to DUI breath or blood testing. (“A person who drives a motor vehicle is deemed to have given his or her consent to chemical testing of his or her blood or breath for the purpose of determining the alcoholic content of his or her blood, if lawfully arrested for an offense allegedly committed in violation of Section 23140, 23152, or 23153...(C) The [breath or blood] testing shall be incidental to a lawful arrest and administered at the direction of a peace officer having reasonable cause to believe the person was driving a motor vehicle in violation of Section 23140, 23152, or 23153.”) But note that the Supreme Court of the United States has held that it is unconstitutional for states to make it a crime to refuse DUI blood (but not breath) testing without a warrant, even after arrest. Birchfield v. North Dakota (2016) 579 U.S. __. 
  2. Title 17 of the California Code of Regulations ("CCR"), beginning at section 1215, regulates California DUI laws regarding forensic analysis of blood and breath testing.
  3. Same.
  4. 17 CCR 1216.
  5. 17 CCR 1219.1(c).
  6. 17 CCR 1219.1(e)(2).
  7. 17 CCR 1219.1.
  8. 17 CCR 1220.2(a)(5).
  9. 17 CCR 1219.
  10. Davenport v. Department of Motor Vehicles (1992) 6 Cal. App. 4th 133. ("We conclude that the Department may rely on that presumption to show that such [DUI blood] test results were obtained in compliance with statutory and regulatory requirements. This presumption affects the burden of proof (Evid. Code, § 660) and in the absence of contradictory evidence is alone sufficient to support a finding. Indeed, under Evidence Code section 606, the licensee has the burden of proof of demonstrating that there was an official failure to comply with applicable statutory and regulatory requirements.")
  11. Vehicle Code 23612(a)(1)(A) VC – Implied consent to DUI breath or blood testing, endnote 1 above.
  12. Vehicle Code 23612(a)(1)(D) VC – Consequences of refusing a post-arrest DUI breath or blood test; Vehicle Code 13353 VC -- License suspension after DUI breath or blood test refusal.
  13. Birchfield v. North Dakota (2016) 579 U.S. __.
  14. Barstow DUI defense attorney Michael Scafiddi is a former police officer who uses the inside knowledge he obtained as a cop to defend clients accused of DUI and other felonies and misdemeanors in the courts of San Bernardino County and Riverside County.
  15. See California v. Trombetta (1984) 467 U.S. 479 (holding the failure to retain breath samples after a DUI breath test does not violate a defendant's constitutional due process rights).
  16. 17 CCR 1219.1(g). ("In order to allow for analysis by the defendant, the remaining portion of the sample [obtained by a DUI blood test] shall be retained for one year after the date of collection.")
  17. 17 CCR 1219.1(g)(2). ("Whenever a sample is requested by the defendant for analysis and a sufficient sample [of the blood drawn in the DUI blood test] remains, the forensic alcohol laboratory or law enforcement agency in possession of the original sample shall continue such possession, but shall provide the defendant with a portion of the remaining sample in a clean container together with a copy or transcript of the identifying information carried on the original sample container.")


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