CrimProf Blog

Editor: Kevin Cole
Univ. of San Diego School of Law

Thursday, April 30, 2020

Thompson & Casarez on Blind Testing and Forensic Sciences

Sandra Guerra Thompson and Nicole B. Casarez (University of Houston Law Center and University of St. Thomas) have posted Solving Daubert’s Dilemma for the Forensic Sciences Through Blind Testing (57 Houston Law Review 617 (2020)) on SSRN. Here is the abstract:
In 1993, in Daubert v. Merrill Dow Pharmaceuticals, Inc., the Supreme Court set forth a multi-factored reliability test for scientific evidence. Of the factors courts should consider in determining the validity of scientific evidence, the Court instructed trial courts to consider the “potential error rate” of the scientific method. In 2009, the National Academy of Sciences, in its landmark report on the state of forensic science, came to this remarkable conclusion: “[N]o forensic method other than nuclear DNA analysis has been rigorously shown to have the capacity to consistently and with a high degree of certainty support conclusions about ‘individualization’ (more commonly known as ‘matching’ of an unknown item of evidence to a specific known source).” Of course, matching items of evidence to a specific known source is the central mission of forensic science, so this critique has led to considerable study and research over the past ten years aimed at developing statistical methods to measure error rates in these disciplines. Yet we have seen little progress in developing a statistical foundation for forensic disciplines, which continues to represent a pressing concern. Without reliable information about how often a forensic science process yields the wrong answer, the probative value of forensic evidence is impossible to quantify.

This Article describes a major breakthrough in developing a statistical foundation for forensic science disciplines: a cutting-edge blind proficiency testing program operating in six disciplines at the Houston Forensic Science Center (HFSC).
By introducing mock evidence samples into the ordinary workflow of its laboratory analysts, HFSC has begun to develop statistical data that will allow it to calculate error rates for those disciplines. We provide specific details regarding how the program operates in HFSC’s toxicology, firearms, and latent prints sections, and discuss both the challenges and benefits the laboratory has experienced because of the blind proficiency testing program. We propose that criminal justice stakeholders should urge other forensic laboratories to implement similar blind proficiency testing programs to develop the statistical data needed to prove the scientific validity of the forensic disciplines.

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