A witness may be impeached by evidence of defects in the witness' intelligence or understanding.

United States v. Alexander, 331 F.3d 116, 121-123 (D.C. Cir. 2003) (upholding trial court's admission of defendant girlfriend's 911 call as an excited utterance because even though "the intervening call might suggest that [the....A statement falls within the hearsay exception created by Federal Rule of Evidence 803(2) or a comparable State rule for excited utterances, only if the declarant (the maker of the statement) was under the stress of the startling event or condition when he or she made the statement that relates to that startling event or condition.

Germano v. International Profit Association, Inc., 544 F.3d 798, 801-805 (7th Cir. 2008) (holding, in plaintiff's civil action against defendant company for violation of the Americans with Disabilities Act, that the trial court erred in ruling that....A statement of an employee or agent is treated as an employer's or principal's statement and, if offered against the employer or principal, it is an admission that is exempt from the hearsay rule if the employer or principal authorized its employee or agent to speak about the matter that the employee or agent spoke about and if the statement was made during the employment or agency relationship.

United States v. Charley, 189 F.3d 1251, 1259-1260 (10th Cir. 1999) (upholding trial court's admission of accused's prior conviction for sex molestation where there was a similarity between accused's prior crime and the present charges).Federal Rule of Evidence 413 and comparable rules in a few States create an express exception to the prohibition against circumstantial use of character, the prohibition against the use of character to show conduct. Rules such as Rule 413 provide that in a criminal trial for sexual assault evidence of the defendant's commission of another offense or offenses of sexual assault is admissible.