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Objective: The present research examined whether concurrent expert testimony (“hot tubbing”) and court appointed testimony reduced adversarial allegiance in clinical experts’ judgments compared with traditional adversarial expert testimony. Hypotheses: We predicted Hypothesis 1: Defense experts would render more not responsible judgments and lower ratings of criminal responsibility than would prosecution experts; Hypothesis 2: Adversarial allegiance effects on experts’ judgments would be heightened for adversarial experts and attenuated for concurrent experts over time; Hypothesis 3: Adversarial and concurrent experts would report higher dissonance than would court-appointed experts and adversarial experts’ ratings would increase over time, concurrent experts’ ratings would decrease, and court-appointed experts’ ratings would remain unchanged. Method: Clinicians and advanced clinical doctoral students conducted simulated criminal responsibility evaluations for the prosecution, defense, or court. We categorized participants as favoring the prosecution or defense based on their preexisting attitudes and randomly assigned them to the adversarial, concurrent, or court appointed expert testimony conditions. Participants completed a dichotomous responsibility judgment, strength of responsibility ratings, and cognitive dissonance measure after initial evidence review (n = 93), report completion (n = 52), and testimony (n = 48). Concurrent experts generated a joint report outlining areas of agreement and disagreement before providing testimony. Results: Concurrent testimony did not eliminate adversarial allegiance. Adversarial and concurrent experts’ perceptions of responsibility did not significantly differ (d = .04, 95% CI [.64, .71]) or change over time; however, prosecution experts—across testimony types—rated the defendant as significantly more responsible than did defense experts (d = 1.87, 95% CI [1.06, 2.67]). Concurrent and adversarial experts did not differ in their reports and minimally differed in testimony content. Conclusions: Experts who initially favored the prosecution or defense showed adversarial allegiance regardless of expert testimony method, and we observed no attenuation of this bias over the course of their case involvement.


Jennifer T. Perillo

Anthony D. Perillo

Nikoleta M. Despodova

Margaret Bull Kovera

Version of record: Perillo, J. T., Perillo, A. D., Despodova, N. M., & Kovera, M. B. (2021). Testing the waters: An investigation of the impact of hot tubbing on experts from referral through testimony. Law and Human Behavior, 45(3), 229–242.



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