Journal of Applied Research in Memory and Cognition 2 (2013) 53–55 Contents lists available at SciVerse ScienceDirect Journal of Applied Research in Memory and Cognition jo u r n al hom ep age: www.elsevier.com/locate/jarmac Commentary Forensic science testing: The forensic filler-control method for controlling contextual bias, estimating error rates, and calibrating analysts’ reports Gary L. Wells ∗ , Miko M. Wilford, Laura Smalarz Psychology Department, Iowa State University, West 112 Lago Hall, Ames, IA 50011, United States a r t i c l e i n f o Article history: Received 22 January 2013 Accepted 24 January 2013 Keywords: Forensic science Forensic testing Contextual bias Forensic error rates A large share of forensic science techniques involving the analy- sis of physical evidence have never been validated scientifically. The National Academy of Sciences (NAS, 2009) concluded that, with the exception of nuclear DNA analysis, no forensic method has been rig- orously shown to consistently and with a high degree of certainty demonstrate a connection between evidence and a specific indi- vidual or source and have not developed evidence-based estimates of error rates. The NAS report also noted that forensic analysts 1 are subject to “contextual bias,” which occurs when the analyst is influ- enced by knowledge about the suspect’s background or other case information. Kassin, Dror, and Kukucka (2013) reviewed basic social and cog- nitive psychology supporting the concern regarding contextual bias and makes a compelling case for the value of psychological science to demonstrate and understand contextual bias in forensic testing. Unfortunately, even if contextual bias were neutralized, it leaves untouched significant problems identified by the NAS report: Is the technique reliable? What is the error rate? Is the analyst com- petent to conduct the procedure? Are analysts overstating their conclusions? Forensic science testing and testimony has prolifer- ated without answers to these questions. In effect, a large share of “forensic science” techniques, almost all of which were devel- oped by people in law enforcement rather than scientists, end up coming down to what we call the “inter-ocular” test in which the ∗ Corresponding author. Tel.: +1 515 201 0431. E-mail addresses: glwells@iastate.edu (G.L. Wells), mwilford@iastate.edu (M.M. Wilford), lsmalarz@iastate.edu (L. Smalarz). 1 We use the term analyst to refer to the forensic scientists, forensic examiners, forensic technicians, and forensic analysts who perform these forensic tests and write the reports. analyst visually examines the evidence and determines whether it is a match, not a match, or is inconclusive. Here, we develop the framework and rationale for a method of forensic testing that we call the “filler-control method. 2 ” We argue that this method, which could theoretically be imposed upon forensic testing systems, could simultaneously resolve the bulk of issues addressed in the NAS report: (1) estimate error rates for both the technique and the individual analyst, (2) help calibrate forensic analysts, (3) quickly jettison fraudulent analysts and junk science, and (4) protect against contextual influences. Importantly, the filler-control method can accomplish all four of these objectives using data generated by actual cases as they unfold. Although oth- ers have alluded to the idea that a filler-control method might guard against contextual influences in forensic testing (Kassin et al., 2013; Saks, Risinger, Rosenthal, & Thompson, 2003), we argue that proper use of the filler-control method as described here can alleviate all four of the above-mentioned problems. The filler-control method is best suited to forensic science tech- niques that involve match judgments. The match domain is a large one that includes fingerprints, tool marks, ballistics, bite marks, hair analysis, fibers, handwriting, shoe prints, and any other test for which an analyst is asked to determine whether a trace sample from a crime scene matches something associated with a suspect. 2 These ideas are based largely on the first author’s American Psychology-Law Society Presidential address given at the American Psychological Association meet- ing in 2006, which was drew heavily from the logic of fillers for eyewitness identification from lineups (Wells, Rydell, & Seelau, 1993). 2211-3681/$ – see front matter © 2013 Society for Applied Research in Memory and Cognition. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jarmac.2013.01.004