Rule 786 Evidence of traits of his character other than honesty or veracity, or their opposites, is inadmissible to attack or support the credibility of a witn…

When a witness testifies in court, the only character traits that matter for judging their credibility are honesty and truthfulness. You cannot bring up other parts of a person's character, good or bad, just to make the jury trust or distrust what they say on the stand.

For example, if a witness has a reputation for being aggressive or generous, that information cannot be used to convince the jury to believe or disbelieve their testimony. The focus stays strictly on whether the person is an honest and truthful individual.