April 20, 2020 Scientific Evidence

“Bullet Points”

Jules Epstein

Does science support a firearms and toolmark expert from saying anything more than that “the firearm may have fired the recovered casing . . . ? Not “it came from this gun and no other” or “casings from the crime scene and from test fires of the suspect’s gun match,” but a much more calibrated and restricted conclusion, evidence that is probative but not determinative.

According to a September 2019 ruling, the “may” finding is the limit. “[T]he government’s expert may testify that based on his examination, the recovered firearm cannot be excluded as the source of the cartridge casing found on the scene of the alleged shooting.“ United States v. Tibbs, No. 2016-CF1-19431, 2019 D.C. Super. LEXIS 9, at *80 (Sept. 5, 2019).

Before delving into Tibbs, some context may be needed. Examining firearms to link a fired projectile or cartridge casing to a specific weapon has been a practice for more than a century. James E. Hamby & James W. Thorpe, The History of Firearm and Toolmark Identification, FirearmsID.com (last visited Nov. 29, 2019). The study of stria, the markings left on projectiles after firing, began in the 1880s.

As one article describes an early effort, “[i]n 1907, the Frankfort Arsenal was able to positively identify thirty-nine out of the forty-five examined cartridge cases to either a Krag rifle or Springfield rifle used in a riot in Brownsville, Texas, through the use of only magnified photographs of firing pin impressions on the spent cartridge cases.” Kathryn E. Carso, Comment, Amending the Illinois Postconviction Statute to Include Ballistics Testing, 56 DePaul L. Rev. 695, 700 (Winter 2007).

Yet distinguishing between cases from two guns of different manufacture is a far cry from linking a projectile or cartridge case to a single firearm and excluding all others, especially in a world where weapons proliferate. In the United States alone, there are more than 300 million firearms. Scott Horsley, Guns in America, by the Numbers, NPR (Jan. 5, 2016).)

The sheer number of weapons has not deterred experts from concluding, and courts allowing testimony, that a particular bullet or cartridge case came from a suspect’s firearm to the exclusion of all other weapons in the world. Yet there have been demonstrated errors in such testimony. As reported in the New York Times on November 28, “Darrell Siggers . . . spent 34 years in prison before . . . his release last year[]. . . . He was convicted based on erroneous testimony from a police officer who said that a bullet in the victim’s body matched one found in Mr. Siggers’s apartment building.” Richard A Oppel Jr. & Farah Stockman, Prosecutors Usually Send People to Prison. These Are Getting Them Out., N.Y. Times (Nov. 28, 2019).

Which brings us to Tibbs. A challenge to the scope of firearms-matching testimony brought by Washington, DC’s Public Defender Service, an office known for its understanding of and commitment to litigating challenges to expert testimony, the Tibbs court heard days of expert testimony and reviewed expert reports. Because the District of Columbia had recently transitioned from the Frye standard to the federal Daubert test, the judge deemed it a chance for a fresh look at this debate.

The decision in some sense speaks for itself, and while it is one of many to confront challenges to firearms-matching evidence, it is one of the few to impose substantial limits. (For recent decisions to the contrary, see United States v. Romero-Lobato, 2019 U.S. Dist. LEXIS 80881, at *3, 2019 WL 2089988 (Nev. May 13, 2019) (collecting cases and approving testimony that “the Taurus handgun found in the stolen Yukon following the police chase is the same gun that was used to fire a round into the ceiling of Aguitas Bar and Grill”).)

What, then, is its importance? First, Tibbs is one of the few cases to actually have an evidentiary hearing with competing expert testimony on the threshold issue of admissibility. It also is one that applies each Daubert criterion with great scrutiny as when, for example, it determines that journals of, by, and for firearms examiners do not constitute true “peer review.” The opinion also offers a meticulous dissecting of studies regarding the “error rate” (or lack of a well-established one) in this field.

There is broader significance. David Kaye has written that “Federal Rule of Evidence 702 has not performed well in regulating the admission of putatively scientific identification methods for associating traces with their possible sources.” David H. Kaye, How Daubert and Its Progeny Have Failed Criminalistics Evidence and a Few Things the Judiciary Could Do About It, 86 Fordham L. Rev. 1639, 1658 (2018). The Tibbs opinion—whether one agrees with its ultimate determination or not—is an exception to that criticism in its diligence and thoroughness. And for anyone involved in investigating, prosecuting, defending, or judging cases involving firearm tracing analysis, it is essential reading.

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Jules Epstein

Jules Epstein is professor of law and director of advocacy programs at Temple Beasley School of Law and served as a member of the National Commission on Forensic Science.