When an exception to the character evidence prohibition makes evidence of a criminal defedant's character admissible, the testimony of a witness on direct examination about the defendant's character must take the form of reputation or opinion and it cannot consist of specific instances of the defendant's conduct.

Tanberg v. Sholtis, 401 F.3d 1151, 1167-1170 (10th Cir. 2005) (holding, in plaintiffs' action against police officer for false arrest, use of excessive force, and assault and battery, that evidence of police officer's other acts was inadmissible where (1) "plaintiffs have failed to establish the relevance...Evidence of a criminal or wrongful act apart from the act that at issue at trial Is not barred by the prohibition against circumstantial use of character if intent, knowledge, mistake, or accident is a legally-material factual issue, the opposing party suggests the non-existence of knowledge or urges mistake or accident as a defense, and evidence of another crime, wrong, or act is offered to prove the knowledge or the absence of mistake or accident by a criminal defendant or other person.

Cf. Crawford v. Washington, 541 U.S. 36, 56 n. 6 (2004) ("The one deviation we have found involves dying declarations. The existence of that exception as a general rule of criminal hearsay law cannot be disputed.....Dying declarations may be exempt from the right of confrontation guaranteed to defendants in both federal and state trials by the Sixth Amendment to the U.S. Constitution.

Blair v. Henry Filters, Inc., 505 F.3d 517, 531 (6th Cir. 2007) (holding, in plaintiff employee's action against defendant employer for age discrimination and hostile work environment, that the trial court properly admitted....A statement by an agent or an employee can be imputed to the principal or the employer (respectively) and be treated as a vicarious admission (that, like other admissions, is exempt from the prohibition against hearsay) only if the statement was made during the agency or employment relationship.