A Demonstrative Helps Opposing Expert Testimony Sensitize Jurors to the Validity of Scientific Evidence

This study examined whether a demonstrative (visual aid) could increase the ability of opposing expert testimony to sensitize jurors to variations in the validity of scientific evidence. Undergraduates (N = 246) viewed a videotaped reenactment of an armed robbery trial with an eyewitness identification as the key evidence. Both the validity of the defense expert’s study on eyewitness identification and the type of opposing expert testimony varied. Although participants were sensitive to the scientific quality of the defense expert’s testimony when an opposing expert addressed the defense expert’s study, regardless of the presence of a demonstrative, jurors’ verdicts were sensitive only when the opposing expert used a demonstrative to communicate about validity issues. Thus, an opposing expert who addresses a defense expert’s study with or without a demonstrative may be sufficient to improve jurors’ understanding of scientific evidence, but the addition of a demonstrative is necessary to translate this knowledge into verdict decisions.