DUI Lawyer | Joel Brand, Esq.

“Rising BAC Defense” to a DUI

In California, driving under the influence (DUI) charges are often based on the blood alcohol concentration (BAC) measured at the time of a traffic stop or shortly thereafter. However, the “rising BAC defense” challenges the reliability of these measurements, arguing that the defendant’s BAC was below the legal limit while driving but increased to an illegal level between the time of driving and the administration of the test. This defense hinges on the understanding of alcohol absorption and metabolism, as well as the timing of the tests relative to the driving event. This article provides a comprehensive analysis of the rising BAC defense, its legal framework, scientific basis, and practical considerations in California DUI cases.

Legal Framework

Under California Vehicle Code § 23152, it is illegal to drive with a BAC of 0.08% or higher. The rising BAC defense argues that the BAC test results are not an accurate reflection of the defendant’s BAC at the time of driving. This defense leverages the physiological process of alcohol absorption, which can cause BAC levels to continue rising after a person has stopped drinking.

The key legal foundation for the rising BAC defense includes:

  1. Timing of the BAC Test: The defense must show that the BAC test was administered during the absorption phase of alcohol metabolism.
  2. Absorption Rate: The defendant’s BAC was still rising at the time of the test due to recent consumption of alcohol.
  3. Extrapolation: Scientific evidence must support the claim that the BAC at the time of driving was below the legal limit, despite a higher BAC at the time of testing.

Scientific Basis

The rising BAC defense is grounded in the science of alcohol absorption and metabolism. After consuming alcohol, it takes time for the alcohol to be absorbed into the bloodstream. The rate of absorption can vary based on several factors:

  1. Amount of Alcohol Consumed: Larger quantities of alcohol take longer to absorb.
  2. Food Intake: Food in the stomach can slow the absorption rate.
  3. Body Weight and Composition: Individual metabolic rates can affect how quickly alcohol is absorbed and processed.

Typically, it takes between 30 minutes to 2 hours for alcohol to be fully absorbed into the bloodstream. During this absorption phase, a person’s BAC will continue to rise. Therefore, if a driver consumed alcohol shortly before being stopped, their BAC might be below the legal limit while driving but could increase by the time the test is administered.

Case Law and Precedents

Several California cases illustrate the application of the rising BAC defense. While each case is unique, they provide insight into how courts evaluate the validity of this defense.

In People v. McNeal (2009) 46 Cal.4th 1183, the California Supreme Court acknowledged the possibility of a rising BAC, noting that expert testimony on alcohol absorption rates could be relevant in challenging DUI charges. This case underscores the importance of scientific evidence in supporting the rising BAC defense.

Another significant case is People v. Ireland (2010) 188 Cal.App.4th 328, where the court allowed expert testimony to demonstrate that the defendant’s BAC was rising at the time of the test. The court held that such evidence could create reasonable doubt about the defendant’s BAC at the time of driving.

Practical Application in DUI Cases

Successfully employing the rising BAC defense requires a strategic approach, combining legal expertise and scientific evidence. Here are the critical steps and considerations:

  1. Timing Analysis: Determine the exact time of the last alcohol consumption, the traffic stop, and the BAC test. This timeline is crucial in demonstrating that the BAC was rising during the test.
  2. Expert Testimony: Engage a forensic toxicologist or medical expert to explain the alcohol absorption process and provide an extrapolation of the BAC at the time of driving. The expert should be able to present complex scientific concepts clearly and persuasively.
  3. Cross-Examination: Challenge the prosecution’s evidence, including the accuracy and timing of the BAC test. This may involve questioning the calibration and maintenance of testing devices, the qualifications of the administering officer, and the procedures followed.
  4. Alternative Explanations: Provide evidence of factors that could have slowed the absorption rate, such as food intake or specific health conditions.

Challenges and Limitations

The rising BAC defense, while scientifically grounded, faces several challenges:

  1. Credibility of Evidence: Courts may scrutinize the credibility of expert witnesses and the scientific basis of their testimony.
  2. Jury Perception: The defense must effectively communicate complex scientific information to a lay jury, which can be challenging.
  3. Counterarguments: The prosecution may present their own experts to refute the rising BAC theory and argue that the defendant’s BAC was above the legal limit while driving.

Conclusion

The rising BAC defense offers a scientifically valid and legally recognized strategy for contesting DUI charges in California. By demonstrating that the defendant’s BAC was still rising at the time of testing and was below the legal limit while driving, defense attorneys can create reasonable doubt and potentially secure a favorable outcome for their clients. However, this defense requires meticulous preparation, credible expert testimony, and a clear presentation of scientific evidence to be effective.

Citations

  • California Vehicle Code § 23152.
  • People v. McNeal (2009) 46 Cal.4th 1183.
  • People v. Ireland (2010) 188 Cal.App.4th 328.