Inconclusives and Error Rates in Forensic Science: A Signal Detection Theory Approach

Hal R Arkes, Jonathan J Koehler, Inconclusives and error rates in forensic science: a signal detection theory approach, Law, Probability and Risk, 2022;, mgac005, https://doi.org/10.1093/lpr/mgac005

Northwestern Public Law Research Paper No. 22-24

38 Pages Posted: 20 Jul 2022 Last revised: 15 Aug 2022

Date Written: May 24, 2022

Abstract

There are times when a forensic scientist may not be comfortable drawing a firm conclusion about whether a questioned sample that appears to contain useful identifying information did or did not come from a particular known source. In such cases, the forensic scientist may call the sample pair “inconclusive.” We suggest that signal detection theory (SDT), which is concerned with the detection of weak signals in noisy environments, provides a useful framework for understanding the role that inconclusives play in the various feature-matching forensic sciences. SDT shows that “inconclusive” is often an appropriate response depending on both the strength of the signal in the samples and the thresholds adopted by the examiner. We also argue that inconclusives should not be coded as either correct or incorrect when tabulating forensic error rates.

Keywords: signal detection theory, forensic science, inconclusive, error rates

Suggested Citation

Arkes, Hal R. and Koehler, Jonathan J., Inconclusives and Error Rates in Forensic Science: A Signal Detection Theory Approach (May 24, 2022). Hal R Arkes, Jonathan J Koehler, Inconclusives and error rates in forensic science: a signal detection theory approach, Law, Probability and Risk, 2022;, mgac005, https://doi.org/10.1093/lpr/mgac005 , Northwestern Public Law Research Paper No. 22-24, Available at SSRN: https://ssrn.com/abstract=4158550

Hal R. Arkes

Ohio State University - Department of Psychology ( email )

240N Lazenby Hall
1885 Neil Avenue
Columbus, OH 43210
United States
614-292-1592 (Phone)
614-688-3984 (Fax)

Jonathan J. Koehler (Contact Author)

Northwestern University - Pritzker School of Law ( email )

375 E. Chicago Ave
Chicago, IL 60611
United States

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