Defence Against the Modern Arts: The Curse of Statistics

EU IAI Webinar @ 3pm CET / 8am CST on February 11th, 2020

Defence Against the Modern Arts: The Curse of Statistics

After decades of publications, conferences, debates and research, there is an exponentially-growing agreement in the forensic community that conclusions should be supported by data. At the core of this new approach lies mathematics, and more specifically statistics and probability theory. Data enables stronger, more valid, inferences, and more transparent conclusions. Whether these conclusions should be supported by error rates or through the use of a likelihood ratio is not the concern of this talk. However, the use of statistical and probabilistic concepts to interpret data may give a varnish of legitimacy to poor data, weak understanding of scientific issues, or flawed methodology.

In this webinar, we will review a series of claims and models, based on data and involving the use of statistics and probability theory, that are advocated to support fingerprint conclusions. The first result involves the interpretation of so-called black-box studies to quantify the error rates of fingerprint examinations: we will explore the flawed PCAST interpretation of the Miami-Dade Police Department study and discuss how the misuse of statistics led to the 1 in 18 false positive error rate claimed in the PCAST report. The second and third results involve two different attempts to quantify the weight of forensic evidence using calculations that have been given the appearance of the Graal: the likelihood ratio: we will expose these two approaches (one in the U.S. and one in the E.U.) and discuss how the misuse of statistics and probability theory leads to algorithms that generate numbers that are either meaningless, or that can be dramatically misleading.

At the end of this webinar, the audience will have the opportunity to question and discuss the points made by the authors.

Cedric Neumann was awarded a PhD in Forensic Science from the University of Lausanne, Switzerland. From 2004 to 2010, Cedric worked at the Forensic Science Service (FSS) in the United Kingdom. As head of the R&D Statistics and Interpretation Research Group, he contributed to the development of the first validated fingerprint statistical model. This model was used to support the admissibility of fingerprint evidence in U.S. courts. Cedric is currently an Associate Professor of Statistics at the South Dakota State University. Cedric’s main area of research focuses on the statistical interpretation of forensic evidence, more specifically fingerprint, shoeprint and traces. Cedric has taught multiple workshops for forensic scientists and lawyers alike. Cedric served on the Scientific Working Group for Friction Ridge Analysis, Study and Technology (SWGFAST), was a member of the Board of Directors of the IAI and is the resident statistician of the Chemistry/Instrumental Analysis SAC committee in the NIST-OSAC.