Battling to a Draw: Defense Expert Rebuttal Can Neutralize Prosecution Fingerprint Evidence

Abstract

The present study examined whether a defense rebuttal expert can effectively educate jurors on the risk that the prosecution’s fingerprint expert made an error. Using a sample of 1716 jury-eligible adults, we examined the impact of three types of rebuttal testimony in a mock trial: (a) a methodological rebuttal explaining the general risk of error in the fingerprint-comparison process; (b) a new-evidence rebuttal concluding the latent fingerprint recovered in this case was not suitable for use in a comparison; (c) a new-evidence rebuttal excluding the defendant as the source of the latent fingerprint. All three rebuttals significantly altered perceptions of the prosecution’s fingerprint evidence, but new-evidence rebuttals proved most effective. The effectiveness of the rebuttals depended, however, on whether jurors were more concerned about false acquittals or false convictions.

Keywords: fingerprint evidence, forensic evidence, juror decision-making, expert testimony, battle of experts, inoculation