The Use of a Filler-Control Method to Calibrate Forensic Evidence Analysis

Since the advent of DNA analysis, organizations such as the Innocence Project have been able to exonerate people who were wrongfully convicted of crimes, often due to erroneous forensic evidence analysis. In many cases, analytical techniques, such as fingerprint analysis, toolmark analysis, or hair comparisons have been cited as nearly infallible sources of evidentiary fact. However, these methods rely on subjective interpretation by a forensic examiner and lack stringent, quantitative methods for ensuring reliability and accuracy. For most of these methods, the examiner is supplied only with the unknown sample from the crime scene, and a known sample from a suspect. This, combined with the influence of psychological factors such as confirmation bias, has resulted in the need for a reliable mechanism of ensuring the efficacy of a particular type of analysis as well as the objectivity, and competence of the analyst. One proposed method to resolve these issues is the use of a filler-control method, in which analysts are given an “evidence line-up” containing at least three samples: the unknown sample from the crime scene, a sample from the suspect, and at least one filler sample from an individual who is not involved in the investigation. This method provides a reliable method for estimating error rates for an analyst and can provide the analyst with direct feedback about their performance to accurately gauge their competence. This method also helps to prevent the introduction of confirmation bias, as the source of the samples is unknown to the analyst. The goal of the current research is to test the capacity of a filler-control method to lead to better confidence-calibration of examiners’ match judgements when compared to the conventional method. The hypothesis of this experiment is that participants using the filler control method will have improved performance and increased confidence calibration due to receiving feedback over the course of the trials when compared to participants using the traditional method.