A person shall not be incompetent as a witness in any court, matter, or proceeding by reason of the person's conviction of a crime. The conviction of a crime involving moral turpitude within 15 years shall be the only crime admissible in evidence given to affect the credibility of a witness. (Amended 1959, No. 250, eff. June 10, 1959; 2005, No. 148 (Adj. Sess.), § 4f.)