(a) Opinion and Reputation Evidence of Character. The credibility of a witness may be attacked or supported by evidence in the form of opinion or reputation, but subject to these limitations:
(1) the evidence may refer only to character for truthfulness or untruthfulness; and
(2) evidence of truthful character is admissible only after the character of the witness for truthfulness has been attacked by opinion or reputation evidence or otherwise.
(b) Specific Instances of Conduct. Specific instances of the conduct of a witness, for the purpose of attacking or supporting the witness’ credibility, other than conviction of crime as provided in Rule 609, may not be inquired into on cross-examination of the witness nor proved by extrinsic evidence.