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Affidavit for the Frye challenge in United States v. Troy Worsley on the "Validity of Firearm and Toolmark Identification" by Dr. Stephen G. Bunch, Firearms-Toolmarks Unit Chief, FBI Laboratory.

Stephen G. Bunch, Erich D. Smith, Brandon N. Giroux, Douglas P. Murphy; Firearms-Toolmarks Unit, FBI Laboratory Quantico, Virginia
The science of firearm and toolmark identification has been a core element in forensic science since the early 20th century. Although the core principles remain the same, the current methodology uses validated standard operating procedures (SOPs) framed around a sound quality assurance system. In addition to reviewing the standard procedure the FBI Laboratory uses to examine and identify firearms and toolmarks, we discuss the scientific foundation for firearm and toolmark identification, the identification criterion for a "match" and future research needs in the science.

This document details the Government's opposition to a defense motion to exclude expert testimony of a firearm "match" to numerous cartridge cases. In the defense motion, elements of this NAS Report were used as the primary basis to exclude this firearm testimony.

NAS Study to address certain issues raised by the computerized ballistic imaging technology.

This affidavit filed in US v. Kevin Edwards where further clarification is given in regards to the relevance between the NAS study and the validity of FA/TM ID.

This motion filed in US v. Monteiro, et al. Information provided by David Lamagna as a defense expert.

This article appeared in The Champion, September/October 2002 authored by Joan Griffin and David Lamagna.

This amicus brief by A. Schwartz was published in the Journal of Philosophy, Science and Law.

After A. Schwartz wrote the above amicus brief she then used it as a basis for publication in the legal literature. This resulted in the paper that appeared in the Columbia Science and Technology Law Review.

Ron Nichols has provided a comprehensive response to the claims made in the A. Schwartz Columbia Science and Technology Law Review article. PowerPoint Summary

This article critically evaluates experiments used to justify inferences of specific source attribution ('individualization') to '100% certainty' and 'near-zero' rates of error claimed by firearm toolmark examiners in court testimonies, and suggests approaches for establishing statistical foundations for firearm toolmarks practice that two recent National Academy of Science reports confirm do not currently exist. Issues that should be considered in the earliest stages of statistical foundational development for firearm toolmarks are discussed.

The forensic practice of firearms-toolmarks identification rests on a currently indefensible conceptual foundation of discernible uniqueness of firearms and tools. However, similar to the now-defunct forensic practice of comparative bullet-lead analysis that had been admitted for almost four decades in judicial proceedings, there has never been any scientifically acceptable hypothesis testing of the underlying premises required for practice validation. Existing studies in the domain literature typically presented in court testimonies as support for specific source attributions are pervasively and fatally flawed such that they have no external validity for extrapolation to universal assumption. They are, thus, of no value for validation of the critical premise of discernible uniqueness in real-world forensic scenarios and are largely irrelevant to any particular criminal judicial proceeding. A practical solution is offered that would allow a scientifically defensible opinion to be proffered to courts until comprehensive and meaningful hypothesis testing can be conducted by the mainstream scientific community.

Stephen Bunch and Gerhard Wevers, Application of Likelihood Ratios for Firearm and Toolmark Analysis, Science and Justice 53 (2013) 223-229

Historically firearm and toolmark examiners have rendered categorical or inconclusive opinions and eschewed probabilistic ones, especially in the United States. We suggest this practice may no longer be necessary or desirable, and outline an alternative approach that is within a comprehensive logical/Bayesian paradigm. Hypothetical forensic and non-forensic examples are provided for readers who are practicing firearm and toolmark examiners, and the strengths and weaknesses of both approaches are considered.