Cross-Examination Educates Jurors About Missing Control Groups in Scientific Evidence

In 2 experiments, we examined the ability of cross-examination to assist mock jurors with assessing the validity of expert evidence about the reliability of eyewitness identifications presented during an armed robbery trial. Participants watched a simulated robbery trial in which an expert described a study examining the effects of stress on eyewitness memory. In both studies, we varied the study's internal validity (valid or missing a control group) and whether the cross-examination educated jurors about the study's validity (scientifically informed or scientifically naive). In Experiment 1, we also manipulated the expert type (adversarial court-appointed, adversarial defense-hired, or inquisitorial court-appointed) and in Experiment 2, we varied court type (adversarial or inquisitorial). Irrespective of expert type or court type, jurors who heard scientifically informed cross-examinations provided lower ratings of scientific validity when the expert's study was missing an appropriate control group than when it was not missing a control group, suggesting that cross-examination may help educate jurors about at least 1 type of internal validity threat.