Reputation or opinion is admissible to impeach a witness by showing the untruthfulness of the witness.

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 who is not authorized to speak on behalf of the agent's principal or the employee's employer may nonetheless be treated as the statement of the principal or the employer and thus as a vicarious admission that is exempt from the prohibition against hearsay; but such a statement can be imputed to the principal or the employer only if the statement, if by an agent, is about a matter within the scope of the agent's agency or, if by an employee, the statement is about a matter within the scope of the employee's employment.

Fed. R. Evid. 611(a) ("The court shall exercise reasonable control over the mode and order of interrogating witnesses and presenting evidence so as to ... (3) protect witnesses from harassment or undue embarrassment.").The trial court has broad discretion to bar abusive, humiliating, and harassing questions.

Perez v. Irwin, 963 F.2d 499, 502 (2d Cir. 1992) ("The Supreme Court in Holland v. United States, 348 U.S. 121, 140, 75 S.Ct. 127, 137, 99 L.Ed. 150 (1954), reh'g denied, 348 U.S. 121, 75 S.Ct. 127, 99 L.Ed. 150 (1955), defined reasonable doubt as a doubt that would cause a person to hesitate to act in...Courts have approved jury instructions saying that a reasonable doubt is a doubt that would cause a reasonable person to hesitate to act before making an important or critical private decision.