(1) Less than twenty-one years of age;
(2) An habitual drunkard;
(4) Addicted to the use of any controlled substance as defined by any of the provisions of chapter sixty-a of this code; or
(5) Mentally incompetent.
(b) It shall be a defense to a violation of subdivision (1), subsection (a) of this section if the seller shows that the purchaser:
(1) Produced written evidence which showed his or her age to be at least the required age for purchase and which bore a physical description of the person named on the writing which reasonably described the purchaser; or
(2) Produced evidence of other facts that reasonably indicated at the time of sale that the purchaser was at least the required age.