This investigation of expert witness gender used scenarios addressing threats to the expert, sexuality, parenting by the expert, and lying, and in which intrusive and non‐intrusive gender cross‐examinations were presented to 352 mock jurors. Male and female experts were matched carefully on attractiveness and other social desirability dimensions. In half of the situations the expert witnesses replied with defensive answers, and in the other half, they replied assertively. The assertive responses were found to be significantly more effective on a number of dependent measures, including perceived credibility. In results consistent with other studies, the male experts were evaluated more positively than the female experts. Sexism and other attitudes of the mock jurors were unrelated to credibility and expert gender. The results are discussed in the context of managing aggressive cross‐examinations, role demands for women in the courtroom, and methodological approaches to the study of expert witness gender. Copyright © 2014 John Wiley & Sons, Ltd.