10.24.020   Determination of alcoholic content.
   A.   In any criminal prosecution for a violation of Section 10.24.010 relating to driving a vehicle while under the influence of intoxicating liquor, the amount of alcohol in the defendant's blood at the time alleged, as shown by chemical analysis of the defendant's blood, urine, breath or other bodily substance, shall give rise to the following presumptions:
      1.   If there was at the time 0.05 percent or less by weight of alcohol in the defendant's blood, it shall be presumed that the defedant was not under the influence of intoxicating liquor;
      2.   If there was at the time in excess of 0.05 percent but less than 0.10 percent by weight of alcohol in the defendant's blood, such fact shall not give rise to any presumption that the defendant was or was not under the influence of intoxicating liquor, but such fact may be considered with other competent evidence in determining the guilt or innocence of the defendant;
      3.   If there was at that time 0.10 percent or more by weight of alcohol in the defendant's blood, it shall be presumed that the defendant was under the influence of intoxicating liquor;
   B.   Percent by weight of alcohol in the blood shall be based upon grams of alcohol per one hundred cubic centimeters of blood.
   C.   The foregoing provisions of this section shall not be construed as limiting the introduction of any other competent evidence bearing upon the question whether or not the defendant was under the influence of intoxicating liquor.
(Ord. 321 Art.  3 § 1(b), 1974).