Evidence: The Limits of Limiting Forensic Firearm-Identification Testimony

Authors

• David L. Faigman, University of California College of the Law, San FranciscoFollow

Abstract

For more than a century, firearm examiners have testified in unequivocal terms that they can match bullets or cartridge cases to a specific firearm, often asserting identification “to the practical exclusion of all other firearms.” These claims were widely accepted in courts and rarely subjected to empirical validation.

Over the past two decades, however, they have come under increasing scrutiny from scientists, legal scholars, and government bodies. In particular, scientific reviews of the research basis for firearms and toolmark identification have found that the data do not support such claims of “individualization.” Examiners can identify the type or class of gun that left the questioned marks but not the specific gun used. Accordingly, some courts limit what examiners can say about an identification, but the courts disagree about how the testimony should be phrased so that juries can properly understand the strength of the evidence of a match. Specifically, should examiners be limited to testifying that the marks in question are “consistent with” the suspect weapon? Or should they be limited further to testifying only that the suspect weapon “cannot be excluded” as the source of the marks? The research reported in this Chapter examines how jurors understand these two alternative wordings and concludes that the later phrasing is better.

Recommended Citation

Faigman, David L. (2026) "Evidence: The Limits of Limiting Forensic Firearm-Identification Testimony," The Judges' Book: Vol. 10, Article 10.
Available at: https://repository.uclawsf.edu/judgesbook/vol10/iss1/10