2.04.310 [Rule 28] How a Witness' Credibility May Be Attacked

(a) The witness' credibility may be attacked or supported by evidence of opinion or reputation, provided the evidence refers to truthfulness or untruthfulness; and evidence of truthfulness is admissible only when it has been attacked by opinion or reputation evidence or otherwise.

(b) Specific instances of conduct of a witness, for the purpose of attacking or supporting his credibility, may only be inquired into on cross examination, concerning the witness' truthfulness or untruthfulness. The Rule does not operate as a waiver of the privilege against self-incrimination.