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    How signature complexity affects expert and lay ability to distinguish genuine, disguised and simulated signatures

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    This study examined how variations in signature complexity affected the ability of forensic document examiners (FDEs) and laypeople to determine whether signatures are authentic or simulated (forged), as well as whether they are disguised. Forty-five FDEs from nine countries evaluated nine different signature comparisons in this online study. Receiver Operating Characteristic (ROC) analyses revealed that FDEs performed in excess of chance levels, but performance varied as a function of signature complexity: Sensitivity (the true-positive rate) did not differ much between complexity levels (i.e., 65% vs. 79% vs. 79% for low vs medium vs high complexity), but specificity (the true-negative rate) was the highest (95%) for the medium complexity signatures and lowest (73%) for low complexity signatures. The specificity of high-complexity signatures (83%) was between these values. The sensitivity for disguised comparisons was only 11% and did not vary across complexity levels. One hundred-one novices also completed the study. A comparison of the area under the ROC curve (AUCs) revealed that FDEs outperformed novices in medium and high-complexity signatures but not low-complexity signatures. Novices also struggled to detect disguised signatures. While these findings elucidate the role of signature complexity in lay and expert evaluations, the error rates observed here may differ from those in forensic practice due to differences in the experimental stimuli and circumstances under which they were evaluated. This investigation of the role of signature complexity in the evaluation process was not intended to estimate error rates in forensic practice.This article is published as Scurich, Nicholas, Miriam Angel, Hal Stern, and William C. Thompson. "How signature complexity affects expert and lay ability to distinguish genuine, disguised and simulated signatures." Journal of Forensic Sciences 69, no. 6 (2024): 2159-2170. https://doi.org/10.1111/1556-4029.15605. Posted with permission of CSAFE.Center for Statistics and Applications in Forensic Evidence (CSAFE), Grant/Award Number: 70NANB15H176 and 70NANB20H01

    Judging Firearms Evidence

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    Firearms violence results in hundreds of thousands of criminal investigations each year. To try to identify a culprit, firearms examiners seek to link fired shell casings or bullets from crime scene evidence to a particular firearm. The underlying assumption is that firearms impart unique marks on bullets and cartridge cases, and that trained examiners can identify these marks to determine which were fired by the same gun. For over a hundred years, firearms examiners have testified that they can conclusively identify the source of a bullet or cartridge case. In recent years, however, research scientists have called into question the validity and reliability of such testimony. Judges have also viewed such testimony with increased skepticism, especially after the Supreme Court set out standards for screening expert evidence in Daubert v. Merrell Dow Pharmaceuticals, Inc. In this Article, we detail over a century of caselaw and examine how judges have engaged with the changing practice and scientific understanding of firearms comparison evidence. We first describe how judges initially viewed firearms comparison evidence skeptically and thought jurors capable of making firearms comparisons themselves—without an expert. Next, judges embraced the testimony as comparison experts offered more specific and aggressive claims, and the work spread nationally. Finally, we explore the modern era of firearms caselaw and research, with an explosion of reported judicial decisions. Judges increasingly express skepticism and adopt a range of approaches to limit in-court testimony by firearms examiners. We conclude by examining lessons regarding the gradual judicial shift towards a more scientific approach towards expert testimony. The more-than-a-century-long arc of judicial review of firearms evidence in the United States suggests that over time, scientific research can displace tradition and precedent to improve the quality of justice.The following is published as Garrett, Brandon L. and Tucker, Eric and Scurich, Nicholas, Judging Firearms Evidence (February 3, 2023). Duke Law School Public Law & Legal Theory Series No. 2023-10, Available at SSRN: https://ssrn.com/abstract=4325329 or http://dx.doi.org/10.2139/ssrn.4325329. Posted with permission of CSAFE
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