Firearms & Ballistics Expert Witness Testimony Rejected for not being based on Empirical Evidence

Firearms & Ballistics Expert Witness Testimony Rejected for not being based on Empirical Evidence

In January 2021, Timothy Davis experienced an unexpected discharge of his Sig Sauer P320 XCarry pistol while exiting his vehicle, resulting in a severe leg injury from a 9mm hollow-point bullet. The circumstances surrounding the incident were unclear, with conflicting accounts in Davis’ deposition. He stated that, while sitting in his vehicle, he holstered the P320, and as he extended his leg, the pistol discharged. Davis insisted that the P320 was fully holstered and secured on his left hip.

However, a police report and an EMT report provided a different version, indicating that Davis was attempting to holster the P320 when the discharge occurred. Regardless, Davis claimed the P320 discharged without a trigger pull, a contention disputed by Sig Sauer.

In January 2021, Plaintiff Timothy Davis claimed that his Sig Sauer P320 XCarry pistol discharged unexpectedly, injuring his leg with a 9mm hollow-point bullet. Davis provided conflicting accounts of the incident: one stating he holstered the gun before exiting the vehicle, and another suggesting he was attempting to holster it when the discharge occurred.

Davis filed a product liability and negligence lawsuit against Sig Sauer, alleging that the P320 lacked external safeties, making it unreasonably dangerous. Gunsmith James Tertin and human factors engineer William Vigilante, serving as expert witnesses, argued that the absence of a manual safety rendered the pistol defective, increasing the risk of accidental discharge. They contended that this defect was the proximate cause of Davis’ injury.

Sig Sauer moved to exclude Tertin and Vigilante’s opinions and sought summary judgment, claiming that without the expert testimony, there was no genuine dispute of material fact, and Davis failed to establish causation.

Firearms & Ballistics Expert Witness

James Tertin is currently the director of research and development for Magnum Research, a firearms manufacturer based in Pillager, Minnesota. In that role, he is responsible for designing and developing new firearms for the company.

He has been a professional gunsmith since graduating in 1972 from the Gunsmithing School at Trinidad State College in Colorado; the oldest gunsmithing school in the United States. Over the past fifty years, he has been awarded seven firearm design patents.

Human Factors Engineering Expert Witness

William Vigilante graduated with a Doctoral of Philosophy and a Master’s of Science in Ergonomics (Human Factors) Psychology and a Bachelor of Science degree in Psychology (Cognitive track). He is also a Certified Professional Ergonomist by the Board of Certification in Professional Ergonomics (#2019). He has more than 25 years of experience in psychological and human factors research with a focus on human-machine interaction, control-display design, product design, hazard identification and mitigation, risk perception, situational awareness, perception-reaction time, and the design and testing of warning systems.

Discussion by the Court

Federal Rule of Evidence 702 governs the admissibility of expert witness testimony. It permits an expert to testify about scientific knowledge if “(a) the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or determine a fact in issue; (b) the testimony is based on sufficient facts or data; (c) the testimony is the product of reliable principles and methods; and (d) the expert has reliably applied the principles and methods to the facts of the case.”

Sig Sauer had challenged the testimony of Tertin and Vigilante on various grounds, asserting that their causation opinions were speculative and lacked reliable foundations. Additionally, Sig Sauer questioned Vigilante’s qualifications to opine on firearm design. Sig Sauer’s primary objective was to exclude Tertin and Vigilante from expressing the view that Davis’ accident might have been prevented with a thumb safety or tabbed trigger safety on the P320.

The Court concurred with Sig Sauer’s argument, finding that neither Tertin nor Vigilante had a reliable factual basis for their causation opinions. Tertin’s opinion, which stated that any single-action firearm without a manual thumb safety is defective, lacked empirical evidence. Tertin suggested that a tabbed trigger “probably would have prevented the accident,” but he admitted to having no information about what caused Davis’ trigger to depress. Tertin performed no analysis on the circumstances of the accident, providing no basis for his conclusion on the lack of a manual safety being the proximate cause. The Court deemed Tertin’s opinion as pure speculation, lacking any factual foundation or empirical evidence, and therefore inadmissible for proving causation.

Vigilante’s opinion faced a similar challenge. He contended that the P320’s lack of an external manual safety made it defective and unreasonably dangerous, attributing it to the unintentional discharge in Davis’ case. According to Vigilante, triggers could move through inertia, foreign object contact, or contact with a body part, but he lacked an opinion on how Davis’ trigger became engaged.

Vigilante admitted to not inspecting Davis’ pistol or holster, relying solely on Davis’ deposition and a sheriff’s report for his understanding of the accident. He did not speak with Davis or review the first responders’ testimony, and no testing or analysis of physical evidence was conducted to validate Davis’ version of the accident. Vigilante’s causation opinion appeared detached from the specific circumstances of Davis’ case, relying on a general conclusion about the P320’s safety without factual support.

Even Vigilante’s generalized conclusions were based on shaky grounds, using anecdotal data from YouTube videos and a memorandum by the United States Immigration and Customs Enforcement Agency. This lack of empirical evidence failed to meet the standards set by Rule 702 for expert testimony. Even if one assumed the absence of a manual safety was a design defect, Vigilante provided no factual basis for concluding that a manual safety would have prevented Davis’ specific accident. Without a thorough investigation into the accident’s circumstances, Vigilante’s causation opinion was deemed too speculative and lacking reliability. Therefore, his expert testimony was precluded.

The Court briefly addressed another argument asserted by Davis in support of admitting the expert testimony of Tertin and Vigilante. Davis compared two recent Orders from other district courts that considered similar motions filed by Sig Sauer. In the Northern District of Georgia, Sig Sauer’s motions were partially denied, while in the Western District of Oklahoma, Sig Sauer’s motions were granted. Davis urged the Court to distinguish the Western District of Oklahoma case, Herman V. Sig Sauer, asserting that the facts in the present case were distinct.

After reviewing both Orders and their supporting records, the Court concluded that Herman was not distinguishable, particularly concerning the reasoning supporting the exclusion of expert testimony by Tertin and Vigilante. Despite the Northern District of Georgia recognizing that the opinions of Tertin and Vigilante were based on the specifics of the incident in that case, the Court found no similar evidence in the present case. Similar to the Herman Court, the Court noted broad conclusions about an alleged defect in Sig Sauer’s P320 applied generally to the case’s facts. Tertin and Vigilante both admitted that the specific circumstances of Davis’ incident weren’t crucial to their opinions. Therefore, as explained above, neither expert could be relied upon to provide an accurate and helpful opinion on what may have caused the injury in Davis’ particular case. Consequently, both experts were precluded from testifying.

With the exclusion of Tertin and Vigilante, Davis found himself without any expert witness to testify regarding the alleged defect and causation. This absence meant that Davis could not demonstrate the existence of a defect and its role in causing his injury. Consequently, his claims lacked an essential element and failed under Kentucky law. As a result, the Court granted Sig Sauer’s motion for summary judgment.


The Case was decided in Defendant, Sig Sauer’s favor after the testimony of both experts, James Tertin and William Vigilante were excluded and Sig Sauer’s motion for summary judgment was granted.

Key Takeaways:

The admissibility of expert witness testimony is governed by Federal Rule of Evidence 702, which sets criteria requiring the expert’s knowledge to assist the trier of fact, be based on sufficient facts and data, use reliable principles and methods, and be reliably applied to the case’s facts. In the case against Sig Sauer, challenges were raised against the expert testimony of Tertin and Vigilante, asserting that their causation opinions were speculative and lacked reliable foundations. Additionally, Vigilante’s qualifications to opine on firearm design were questioned. The Court, agreeing with Sig Sauer’s arguments, found that neither expert had a reliable factual basis for their causation opinions, rendering them inadmissible under Rule 702 due to a lack of empirical evidence and factual support. Both experts were criticized for offering broad conclusions about an alleged defect in Sig Sauer’s P320, which were then applied generally to the case’s facts, leading the Court to deem their opinions speculative and lacking a specific connection to the incident in question. Vigilante’s reliance on anecdotal data and Tertin’s admission of no empirical evidence were cited as failures to meet the standards set by Rule 702, which requires a reliable basis for expert opinions. Attempts by the Plaintiff to distinguish the present case from others with varying outcomes were rejected by the Court, emphasizing the lack of similar evidence showing the experts’ opinions were based on the specific circumstances of the incident. With the exclusion of expert testimony, the Plaintiff was unable to demonstrate the existence of a defect and causation, resulting in the failure of claims under Kentucky law. As a consequence, the Court granted Sig Sauer’s motion for summary judgment, underscoring the critical role that expert testimony can play in product liability cases.

Case Details:

Case Caption Davis v. Sig Sauer, Inc.
Docket Number3:22cv10
CourtUnited States District Court for the Eastern District of Kentucky, Central Division
Citation2024 U.S. Dist. LEXIS 1796
Order DateJanuary 4, 2024


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