(a) Upon the trial of any criminal action, or preliminary proceeding in a criminal action, arising out of acts alleged to have been committed by any person while driving a vehicle while under the influence of an alcoholic beverage in violation of subdivision (a) of Section 23152 or subdivision (a) of Section 23153, the amount of alcohol in the person’s blood at the time of the test as shown by chemical analysis of that person’s blood, breath, or urine shall give rise to the following presumptions affecting the burden of proof:

(1) If there was at that time less than 0.05 percent, by weight, of alcohol in the person’s blood, it shall be presumed that the person was not under the influence of an alcoholic beverage at the time of the alleged offense.

(2) If there was at that time 0.05 percent or more but less than 0.08 percent, by weight, of alcohol in the person’s blood, that fact shall not give rise to any presumption that the person was or was not under the influence of an alcoholic beverage, but the fact may be considered with other competent evidence in determining whether the person was under the influence of an alcoholic beverage at the time of the alleged offense.

(3) If there was at that time 0.08 percent or more, by weight, of alcohol in the person’s blood, it shall be presumed that the person was under the influence of an alcoholic beverage at the time of the alleged offense.

(b) Percent, by weight, of alcohol in the person’s blood shall be based upon grams of alcohol per 100 milliliters of blood or grams of alcohol per 210 liters of breath.

(c) This section shall not be construed as limiting the introduction of any other competent evidence bearing upon the question of whether the person ingested any alcoholic beverage or was under the influence of an alcoholic beverage at the time of the alleged offense.

(Added by Stats. 1998, Ch. 118, Sec. 84. Effective January 1, 1999. Section operative July 1, 1999, pursuant to Section 23675.)