by William Weinberg on Sep. 09, 2020

Criminal DUI-DWI 

Summary: What is voluntary consent in the context of the requirement to provide a sample in a DUI investigation?


A person who is lawfully arrested (not just detained) on suspicion of driving under the influence has already given the state consent to a blood or breath test under the implied consent law.   Section 23612 of the California Vehicle Code presumes advance consent by the very act of driving on a California road. However, if the driver refuses to submit the chemical test, that refusal has consequences.  If the driver refuses a chemical test and that driver is subsequently convicted of driving under the influence, the penalties will be greater (including mandatory jail time and additional DUI education classes) and the driver will be subject to a mandatory suspension of his or her driving privileges for an extended period of time. This applies only to a breath test as the United States Supreme Court has held that a blood draw is a search subject to the Fourth Amendment. In other words, a blood draw without a warrant or voluntary consent or another recognized Fourth Amendment exception is not lawful. There are several exceptions to the Fourth Amendment, most pertinent here, are the good faith and exigency exceptions. 

Here are a couple of examples where the Fourth Amendment would come into play in a DUI arrest:

Peter is stopped by the police on suspicion of driving under the influence. Peter refuses to the field sobriety tests and the preliminary breath test. All perfectly within his rights to do if he has not yet been arrested for DUI. However, the officer notes that Peter reeks of alcohol and his words are slurred so the officer places him under arrest for suspicion of driving under the influence. Now, the officer informs Peter that he must submit to chemical testing, either blood or breath. Peter chooses a blood test. The blood test shows that Peter’s BAC is .16%, well over the DUI limit. Peter’s attorney files a motion to suppress the blood test results on the grounds that Peter did not give his voluntary consent to the test. Why? Peter argues that the officer failed to fully inform him of the consequences of refusing the test. In other words, Peter assumed that he had to submit to the test. While this is true of the breath test, once Peter chose a blood test, that test required his voluntary consent. Since Peter thought he was mandated to take the test, he argued that he was coerced into the test and thus his consent was not voluntary.

The scenario above was an actual California case. The appellate court held that although the officer gave Peter incomplete information, Peter’s consent was nonetheless voluntary. The court reasoned that "failure to communicate the consequences of refusing a chemical test did not make [the officer's] statement any more or less coercive than if the information had been provided" because in "neither case is the driver advised of his or her right to refuse to test altogether." (People v. Balov (2018) 23 Cal.App.5th 696, 704.) This may be viewed as a good faith exception to the Fourth Amendment. 

Or consider the case of Marcus. Marcus was driving his vehicle when he flipped his vehicle.  He was seriously injured and rendered unconscious. When the paramedics and police officers arrived, they discovered evidence that Marcus had been driving under the influence. Since Marcus was unconscious, he was incapable of giving consent and furthermore, the police cannot arrest an unconscious person. However, under the exigent circumstances, the subsequent BAC blood draw conducted on the unconscious Marcus may be lawful under the Fourth Amendment. However, if there is sufficient time to obtain a warrant for the blood draw, the failure to obtain such a warrant could render the blood draw for BAC unlawful. And that is exactly the circumstances and ruling in the 2016 case, People v. Arredondo (2016) 245 Cal.App.4th 186.

These above scenarios are but two examples of the complicated legal questions that may arise under the implied consent/refusal laws.  Often the outcome will depend on the very specific case facts. An experienced DUI attorney familiar with the courts often changing interpretations of these law will review each DUI case for a potential defense that is not obvious to the “naked eye.” 

Orange County DUI defense attorney William Weinberg has helped hundreds of his DUI clients who have come through his doors in his over 25 years of DUI defense. Mr. Weinberg views each DUI case and client as unique, never taking a cookie-cutter approach to the defense of his cases. He offers a free evaluation of your DUI case and will assess your options and potential defenses. He may be reached by calling his Irvine office at 949-474-8008 or by emailing him at


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