The impact of proficiency testing information and error aversions on the weight given to fingerprint evidence

Fingerprint examiners regularly participate in tests designed to assess their proficiency. These tests provide information relevant to the weight of fingerprint evidence, but no prior research has directly examined how jurors react to proficiency testing information. Using a nationally representative sample of American adults, we examined the impact of proficiency testing information on the weight given to the opinions of fingerprint examiners by mock jurors considering a hypothetical criminal case. The fingerprint examiner's level of performance on a proficiency test (high, medium, low, or very low), but not the type of error committed on the test (false positive identifications, false negative identifications, or a mix of both types of error), affected the weight that jury-eligible adults gave to an examiner's opinion that latent fingerprints recovered from a crime scene matched the defendant's fingerprints, which in turn affected judgments about the defendant's guilt. Jurors who had no information about proficiency gave similar weight to the testimony as jurors exposed to highly proficient examiners, suggesting that jurors assume fingerprint examiners perform at high levels of proficiency unless informed otherwise. We also found that a plurality of Americans deems false acquittals just as aversive as false convictions and a significant minority deems false acquittals more serious. These differences in error aversions predicted differences in evidentiary assessments, suggesting that error aversions of jurors may play an important role in criminal trials.