There are two different types of DUI offenses that may be charged, depending on whether the person had a blood alcohol content below .08 percent or at or above the .08 percent. BAC is measured by the grams of alcohol per 100 milliliters of blood or grams of alcohol per 210 liters of breath. BAC is tested by way of blood tests or by breath tests which use fuel cell and infrared technology.
BAC below .08 percent
A BAC below the per se legal driving limit of .08 percent can be charged as a violation of California Vehicle Code section 23152(a).
"Under the influence" is defined as: A person is under the influence of an alcoholic beverage when as a result of drinking the beverage, using the drug, or both, his or her physical or mental abilities are so impaired that he or she no longer has the ability to drive a vehicle with the caution characteristic of a sober person of ordinary prudence under the same or similar circumstances. If it is established that a person is driving a vehicle under the influence of an alcoholic beverage, it is no defense that another cause also tended to impair his or her ability to drive with the required caution, such as evidence of loss of sleep, epilepsy, diabetes, or injury.
BAC at or above .08 percent-Per Se DUI violation
A BAC at or above .08 percent can be charged as a violation of California Vehicle Code section 23152(b). Note: California can charge and convict the DUI offender of both the "(a)" and "(b)" counts, however one can only be punished for one, not both.
"Under the influence" is defined as: If the evidence establishes beyond a reasonable doubt that at the time of the chemical analysis of the defendant's blood, breath, or urine, there was 0.08 percent or more by weight of alcohol in the defendant's blood, the trier of fact may, but need not, infer that the defendant was under the influence of an alcoholic beverage at the time of the alleged offense.
Sufficiency of Circumstantial Evidence
Circumstantial evidence is evidence that, if found to be true, proves a fact from which an inference of the existence of another fact may be drawn. An inference is a deduction of fact that may logically and reasonably be drawn from another fact or group of facts established by the evidence.
A finding of guilt may not be based on circumstantial evidence alone, unless the proved circumstances are not only: 1) consistent with the theory that the defendant is guilty of the crime, but 2) cannot be reconciled with any other rational conclusion.
Importantly, if the circumstantial evidence permits two reasonable interpretations, one of which points to the defendant's guilt and the other to defendant's innocence, the jury must adopt that interpretation that points to the defendant's innocence, and reject that interpretation that points to guilt.