Does the Forensic Filler-Control Method Reduce Examiner Overconfidence? An Experimental Investigation Using Mock...

Examiner overconfidence is a persistent challenge in the field of forensic science, where testimony overstating the validity of forensic techniques has contributed to numerous wrongful convictions. Scholars have proposed a new method for reducing examiner overconfidence (i.e., subjective confidence that exceeds objective accuracy): the forensic filler-control method. The forensic filler-control method, which includes known non-matching "filler" samples alongside the suspect's sample, is theorized to reduce examiner overconfidence through the provision of immediate error feedback to examiners following match judgments on fillers. We conducted two experiments that failed to yield support for this claim. Among both an undergraduate student sample (Experiment 1) and a forensic science student sample (Experiment 2), the filler-control method was associated with worse calibration (C) and greater overconfidence (O/U) in affirmative match judgments than the standard method. Moreover, the filler-control method produced less accurate non-match judgments, undermining the exonerating value of forensic analysis (i.e., NPV). However, the filler-control method's ability to draw false positive matches away from innocent-suspect samples and onto fillers produced more reliable incriminating evidence (i.e., PPV) compared to the standard procedure. Our findings suggest that neither the standard procedure nor the filler-control procedure offers a uniformly superior method of conducting forensic analysis. We suggest alternative procedures for enhancing both the inculpatory and exculpatory value of forensic analysis.