Blood tests are a common way to measure and prove your BAC level after a DUI arrest. However, they are prone to various errors and can be challenged in court.
In California, the testing procedures for DUI blood draws are set forth in Title 17 of the Code of Regulations.1 If these rules are violated, the results may be invalid.
Mistakes that can produce unreliable blood alcohol concentration (“BAC”) results include:
- Contamination after the sample is collected,
- Switched or intermingled samples, or
- Fermentation, which can cause the sample to produce alcohol inside the vial.
The following chart compares evidentiary breath tests and blood tests in DUI cases.
| DUI Blood Tests | DUI Breath Tests | |
| Accuracy | Generally more accurate | Less accurate, can be affected by acid reflux, GERD, mouth alcohol, and more |
| Invasiveness | Invasive, requires blood draw | Non-invasive, requires breathing into a device |
| Time to results | Longer, typically weeks | Immediate results |
| Administration | Requires medical professional | Can be administered by law enforcement |
| How it measures alcohol | Direct measurement of blood alcohol content (BAC) | Estimates BAC based on breath alcohol content |
| Detects drugs? | Yes | No |
| Retention of sample | Sample can be retained for future testing | No sample retention |
| Refusal consequences | Driver’s license suspension | Driver’s license suspension |
To help you better understand DUI blood samples and testing, our California DUI defense lawyers discuss the following, below:
- 1. When is a DUI blood test required?
- 2. Should I take a DUI blood test or breath test?
- 3. What are the Title 17 regulations?
- 4. Are blood test results presumed to be valid?
- 5. Can police force me to take a blood test?
- 6. Can I have my blood tested in an independent laboratory?
- 7. How can the results be challenged in court?
- Additional Reading
Many experts consider blood tests the most accurate way to measure blood alcohol concentration (BAC).
1. When is a DUI blood test required?
If you drive in California, you are deemed to have consented to take a blood test or breath test if you are arrested for driving under the influence. 1 2 This is known as California’s “implied consent law.”
Usually, you must be given the choice of whether to take a breath or a blood test.3 Exceptions are when:
- The officer has reasonable cause to believe you were driving under the influence of a drug (“DUID”), in which case a blood test can be required;4
- You are unconscious (or the driver is deceased);5 or
- You have been taken to a medical facility where breath testing equipment (a breathalyzer) is not available.6
2. Should I take a DUI blood test or breath test?
Most people elect to take a breath test because it is faster and less invasive. (Note that you may also be asked to undergo a mouth swab test as part of the investigation.)
Though not everyone can take a breath test. For instance, if you have medical problems such as asthma or emphysema, you may not be able to blow hard enough.
Alternatively, you may be unconscious either from alcohol and/or drugs or as the result of an accident.
Differences Between the Tests
Blood tests directly measure the amount of alcohol in your bloodstream. Meanwhile, breath testing devices measure the amount of alcohol in your deep lung air: The machine then mathematically converts this to an approximately equivalent BAC.
The formula for this conversion (known as a “partition ratio”) is fixed by law. In reality, every individual’s partition ratio is different. So, some people consider blood tests a more accurate measure of BAC than breath tests.7
Also, with a blood test, a portion of the sample can be saved for later retesting, as discussed in Section 6, below. This is the major advantage of taking a blood test for BAC rather than a breath test.
3. What are the Title 17 regulations?
Title 17 of the California Code of Regulations sets forth the procedures that govern DUI chemical tests. Under Title 17, regulations that apply to the testing of blood include:
- A specified technician or medical professional must draw the sample as soon as possible after an alleged offense.8
- The draw site must be sterilized with something other than an alcohol-based product (to avoid adding external alcohol to the sample).9
- There must be an anticoagulant and a preservative in the vial to prevent contamination and/or clotting.10
- Any reusable equipment may not be cleaned with or kept in alcohol or other volatile organic solvents.11
- The identity and integrity of the sample must be maintained throughout each step so that chain-of-custody is recorded and undisturbed.12
If any of these or other protocols are not followed, the accuracy of the blood test may be compromised.
4. Are blood test results presumed to be valid?
Under California law, there is a presumption that blood-alcohol results were properly obtained. This means the burden is on you to establish that Title 17 procedures were NOT complied with.13
Though even when Title 17 procedures are not complied with, a blood draw is not necessarily invalid. It all depends on whether your constitutional rights were violated.14
Example: Carl is pulled over for a broken taillight. The officer smells alcohol and asks Carl to take a Preliminary Alcohol Screening (“PAS”) breath test. After Carl blows a .09%, the officer arrests him for Vehicle Code 23152(b).
After his arrest, Carl’s sample is drawn by a medical assistant.15 The test results show a BAC of .10%. Since medical assistants are not authorized by law to do DUI blood draws, Carl’s criminal defense lawyer brings a motion to suppress evidence.16
However, the court finds that the assistant was trained to do blood draws and had done over 100 of them. As a result, even though the regulations were not followed, Carl’s constitutional rights were not violated. His arrest is deemed valid.17
In California, DUI blood draws must be done with your consent or a warrant.
5. Can police force me to take a blood test?
Warrantless Draws
With few exceptions, the police cannot take blood against your will unless they have a warrant. This is true even if the police reasonably suspect you of drug use.
This is because of the United States Supreme Court Birchfield v. North Dakota.18 In Birchfield, the court held that the Fourth Amendment permits warrantless breath tests after a drunk driving arrest, but not warrantless blood tests.
However, Birchfield‘s holding applies only to laws that make it a crime to refuse a chemical test after a drunk driving arrest. California law does not make this a crime. California’s only consequences for a refusal are:
- An enhanced penalty if you are convicted of driving under the influence, and
- A mandatory administrative driver’s license suspension by the California Department of Motor Vehicles (regardless of the outcome of your criminal case).
So it remains for California courts to decide if these penalties are unconstitutional after Birchfield.
Blood Tests with a Warrant (Forced Draws)
With a warrant, an officer can physically force you to submit to a blood test. An officer may seek a warrant if they believe you are under the influence of drugs.
In this situation, you will be taken to a nearby hospital or medical facility. If necessary, you will be restrained by as many officers as it takes so that a lab technician can obtain your sample.
The police may also get a warrant for a forced draw if you are unconscious. Warrants are also necessary if the driver is deceased.
6. Can I have my blood tested in an independent laboratory?
Yes.
With a breath test, no portion of the sample is saved.19 However, Title 17 requires police to retain a portion of your blood for one year after collection.20 (If the driver is deceased, this period is reduced to 90 days).21
The police lab must then make it available to you if you wish to have it independently retested.22 To exercise this right, we would file a blood split motion to have your sample analyzed by a private laboratory of your choosing.
An independent lab might conclude that the sample:
- Showed a lower BAC than .08%,
- Had fermented or been contaminated,
- Was improperly refrigerated or handled, or
- Was otherwise affected in a way that might cast doubt on the police lab’s conclusions.
7. How can the results be challenged in court?
We have two main strategies for challenging DUI blood test results:
- File a motion to exclude the test results from evidence, or
- Aggressively attack law enforcement’s conclusions in an effort to get a plea bargain or a “not guilty” verdict at jury trial.
We will pursue one or both of these strategies along with other defenses such as:
- Rising blood alcohol, or
- Lack of probable cause for a traffic stop.
If you were the victim of a forced draw, we will be extra vigilant. As drunk driving defense attorney Michael Scafiddi23 explains:
“It’s very likely that a rushed or otherwise unexpected blood draw could involve bad protocol. These are mistakes that could ultimately vindicate my wrongfully accused client because they raise a reasonable doubt.”
Additional Reading
For more in-depth information, refer to these scholarly articles:
- Delays in DUI blood testing: Impact on cannabis DUI assessments – Traffic Injury Prevention.
- Variability of the Blood/Breath Alcohol Ratio in Drinking Drivers – ASTM Journal of Forensic Sciences.
- Breath and Blood Alcohol Concentration Measurement in DUI Cases – Forensic Metrology.
- Drunk Driving, Blood, and Breath: The Impact of Birchfield v. North Dakota – Cornell Journal of Law & Public Policy.
- Drunk Drivers and Vampire Cops: The Gold Standard – New England Journal on Criminal and Civil Confinement.
Legal Resources:
- See, in particular, 17 California Code of Regulations (“CCR”) 1219.1.
- California Vehicle Code 23612(a) (1) VC
- Vehicle Code 23612 (a)(2)(B)
- Vehicle Code 23612 (a)(2)(C)
- Vehicle Code 23612(a)(5)
- Vehicle Code 23612(a)(3)
- But some studies have found that the greatest predictor of accuracy is how soon after an arrest a test is given. See, for example, Roiu, Birngruber, Spencer, Wollersen, Dettmeyer and, Verhoff, “A comparison of breath- and blood-alcohol test results from real-life policing situations: a one-year study of data from the Central Hessian police district in Germany,” and Gainsford, Fernando, Lea, and Stowell, “A large-scale study of the relationship between blood and breath alcohol concentrations in New Zealand drinking drivers.”
- 17 CCR 1219.1(a).
- 17 CCR 1219.1(b).
- 17 CCR 1219.1(d)(2)
- 17 CCR 1219.1(c).
- 17 CCR 1219.
- See, for instance, Davenport v. Department of Motor Vehicles (1992) 6 Cal. App. 4th 133. (holding that drivers bear the burden of proving a failure to comply with applicable statutory and regulatory requirements in California DMV DUI license suspension hearings.)
- People v. Esayian (2003) 112 Cal.App.4th 1031. (“Clearly a blood draw is a medical procedure and must be conducted in keeping with medical requirements for such procedure. The Vehicle Code creates a statutory scheme for such draws, but noncompliance with the statute does not, by itself, demonstrate the methods used were improper.”)
- See Vehicle Code 23612(a) (1) VC, California’s “implied consent” law. This law requires drivers to submit to a breath or blood test to test their blood alcohol content if they are lawfully arrested for driving under the influence.
- See Schmerber v. California (1966) 384 U.S. 757. See also People v. McKay (2002) 27 Cal.4th 601 (holding that violation of a statute does not render an arrest unreasonable within the Fourth Amendment and that such statutory violations cannot serve as the basis for the application of the exclusionary rule.) See also People v. Ford (1992) 4 Cal.App.4th 32 (holding that the taking of blood without informed consent does not compel exclusion of the blood test results unless the manner in which the sample was obtained rendered the procedure constitutionally impermissible.
- Facts based on People v. Esayian, endnote 14.
- Birchfield v. North Dakota (2016) 136 S.Ct. 2160.
- See California v. Trombetta (1984) 467 U.S. 479 (holding that failure to retain breath samples after a DUI breath test does not violate a defendant’s constitutional due process rights). See our article on Trombetta Motions.
- 17 CCR 1219.1(f).
- 17 CCR 1219.1(f)(1).
- 17 CCR 1219.1(f)(2).
- Barstow DUI defense attorney Michael Scafiddi is a former police officer who uses his inside knowledge of police procedure to defend clients accused of DUI and driving offense in courts and DMV hearing offices throughout San Bernardino, Riverside, Los Angeles, Orange, and Ventura counties.