California DUI Blood Testing: Contamination & Error

When you drive in California, you give your implied consent to be chemically tested for blood alcohol levels (“BAC”) if you are arrested for a DUI. Generally, either blood or breath is tested for BAC.

DUI blood testing is thought to be more reliable than DUI breath testing. In addition, a breath test is immediate. When it is done, there none of the sample is retained. A blood sample, however, is kept by the crime lab. This allows you to obtain a portion of that sample to have it independently tested and analyzed.

But even blood samples are subject to error and contamination. If not collected or preserved properly, blood tests can lead to an innocent person to being convicted of DUI. This happens frequently.

Mistakes that can make blood tests unreliable indicators of BAC include (but are not limited to):

  • 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

To prevent this, California laws set forth detailed procedures for every step involved in taking and analyzing DUI blood samples.

If any of these protocols are not adhered to, the results of a DUI blood analysis may have been compromised. Therefore, they are open to challenge.


Hemolysis is the breakage of the red blood cells' membranes. It is a common occurrence in blood samples, which can cause fermentation and compromise a laboratory's determination of BAC. Hemolysis can be seen by a rosy or reddish tinge in serum or plasma, as in the sample at the right.

We are a firm whose attorneys include former cops and former DUI prosecutors. We know how to spot problems with DUI blood test results. And when we find errors, we can often use them to get DUI charges reduced or dismissed.

To help you better understand DUI blood testing, our California DUI defense attorneys discuss the following, below:

1. California laws re DUI blood
testing procedures
2. Forced blood draws in California
DUI Cases
3. Retesting the blood in an
independent laboratory

You may also find helpful information in our related articles on California Vehicle Code 23152b Driving with a BAC of 0.08%; DUI Breath Testing; Rising Blood Alcohol -- A DUI defense; Violations of California's Title 17 DUI Chemical Testing Procedures; DUI Chemical Test Refusals; and DUI Defenses.

1. California laws re DUI blood testing procedures

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.

Such rules include (but are not limited to):

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

If these protocols are not strictly adhered to, accuracy of the DUI blood test may be compromised.

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 to establish that there was a flaw in the testing. This is just one reason why it is important to retain an experienced California DUI defense attorney.

Depending on the severity of the botched procedures, your attorney may either:

  • prevail in a motion to have the evidence of the blood sample thrown out of court, or
  • aggressively attack your BAC results in an effort to secure your acquittal.
2. Forced blood draws in California DUI Cases

When you drive in California, you implicitly agree to chemical testing for BAC if you are lawfully arrested for a DUI. This is what's often referred to as California's "implied consent law.”

If you refuse a DUI chemical blood or breath test after an arrest for a misdemeanor DUI, the arresting officer will merely note your refusal.

But if you have been involved in an accident, the arresting officer may seek a warrant for a forced blood draw. 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.

In either case, refusal to submit to a chemical test will result in suspension of your driver's license for one or more years. You will also be subject to an enhanced California DUI penalty.

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 Michael Scafiddi, a well-known Barstow CA DUI defense attorney 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. Retesting the blood in an independent laboratory

DUI blood testing has one major advantage over a breath test. Breath analysis is instant. When you submit to a DUI breath test, no portion of the sample is saved.

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.

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.”

Blood splits allow independent laboratories to evaluate blood samples. An independent lab might conclude 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, especially when coupled with other DUI defenses such as:

Call us for help…

If you or loved one is in need of help with blood tests and you are looking to hire an attorney for representation, 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, or contact our local attorneys at one of our Nevada law offices, located in Reno and Las Vegas.

Legal References:

    1. California Vehicle Code 23612(a)(1)(A) -- 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.
    2. As of January 1999, a urine test is no longer available unless:   
      • the officer suspects you were driving under the influence of drugs or a combination of drugs and alcohol,
      • both the blood and breath tests are not available,
      • you are a hemophiliac, or
      • you are taking anticoagulant medication in conjunction with a heart condition.

See California Vehicle Code 23612 and California Department of Motor Vehicles, Arrest for Driving Under the Influence DUI General Information.

    1. Most forensic toxicologists believe laboratory DUI blood tests have an inherent range of error of about .005 % BAC; while breath test instruments have an inherent range of error of about .01% to .02%. But this is an inherent range of error. Failure to follow strict protocols can magnify this error many fold. See, for example, Sidney Kaye, The Collection and Handling of the Blood Alcohol Specimen American Journal of Clinical Pathology, Vol. 74, No. 5, November 1980.
    2. 17 California Code of Regulations (“CCR”) 1219.1(g) -- In order to allow for analysis by the defendant, the remaining portion of the sample shall be retained for one year after the date of collection.
    3. See endnote 3.
    4. Title 17 of the California Code of Regulations, beginning at section 1215, regulates California DUI laws regarding forensic analysis of blood and breath testing.
    5. Our California criminal defense attorneys have local Los Angeles law offices in Beverly Hills, Burbank, Glendale, Lancaster, Long Beach, Los Angeles, Pasadena, Pomona, Torrance, Van Nuys, West Covina, and Whittier. We have additional law offices conveniently located throughout the state in Orange County, San Diego, Riverside, San Bernardino, Ventura, San Jose, Oakland, the San Francisco Bay area, and several nearby cities.
    6. 17 CCR 1216.
    7. 17 CCR 1219.1(c).
    8. 17 CCR 1219.1(e)(2).
    9. 17 CCR 1219.1.
    10. 17 CCR 1220.2(a)(5).
    11. 17 CCR 1219.
    12. See endnote 3.
    13. California Evidence Code 664 -- It is presumed that official duty has been regularly performed. This presumption does not apply on an issue as to the lawfulness of an arrest if it is found or otherwise established that the arrest was made without a warrant.

See also Davenport v. Department of Motor Vehicles (1992) 6 Cal. App. 4th 133, 7 Cal. Rptr. 2d 818 (“The central issue of the appeal is whether the Department can rely upon the rebuttable presumption contained in Evidence Code section 664 to satisfy its burden of proof at a hearing under section 13558 as to the reliability of chemical test results offered to prove the licensee was driving with a blood-alcohol concentration that violated section 13353.2.”).

    1. California Evidence Code 660. The presumptions established by this article, and all other rebuttable presumptions established by law that fall within the criteria of Section 605, are presumptions affecting the burden of proof.

See also Davenport v. Department of Motor Vehicles, previous endnote (“We conclude that the Department may rely on that presumption to show that such 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. We further conclude that due process is not offended by this allocation of the burden in license suspension proceedings.”).

  1. California Vehicle Code 23612, endnote 1, above. Because you have impliedly consented to these tests, you do not have the right to contact an attorney prior to submitting to a blood or breath test. See California Vehicle Code 23612(a)(4).
  2. In Missouri v. McNeely, 569 U. S. ____ (2013), the United States Supreme Court held that the government's general interest in preventing drunk driving does not justify departing from the requirement of a search warrant absent a showing of exigent circumstances that make securing a warrant impractical in a particular case. The mere fact that BAC dissipates quickly does not, in and of itself, constitute exigent circumstances that justify an exception to the search warrant requirement for nonconsensual blood testing in drunk-driving investigations. The relevant factors in determining whether a warrantless search is reasonable include the practical problems of obtaining a warrant within a timeframe that still preserves the opportunity to obtain reliable evidence.
  3. California Vehicle Code 23612(a)(5).
  4. California Vehicle Code 13353.
  5. California Vehicle Code 23578 -- In addition to any other provision of this code, if a person is convicted of a violation of VC 23152 or VC 23153 [DUI], the court shall consider a concentration of alcohol in the person's blood of 0.15 percent or more, by weight, or the refusal of the person to take a chemical test, as a special factor that may justify enhancing the penalties in sentencing, in determining whether to grant probation, and, if probation is granted, in determining additional or enhanced terms and conditions of probation.
  6. Barstow DUI defense attorney Michael Scafiddi is a former police officer. He represents people accused of DUI throughout San Bernardino County.
  7. See California v. Trombetta (1984) 467 U.S. 479 (holding the failure to retain breath samples does not violate a defendant's constitutional due process rights).
  8. 17 CCR 1219.1(g)(2) -- Whenever a sample is requested by the defendant for analysis and a sufficient sample 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.
  9. See endnote 3.
  10. The “rising blood” defense is also known as the "on the rise" defense. It is used to attack charges of California Vehicle Code 23152b VC "driving with a BAC of 0.08%" by acknowledging that even though your BAC may have been above the legal limit at the time of your DUI blood or breath test, it may have been below that level at the time of driving.

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