This is a products liability case arising from an alleged injury caused by an air rifle. Plaintiff Brian Cornwell (“Cornwell”) ordered an air rifle from Extreme Big Bore Air Rifles on March 25, 2021. After regularly using the rifle for nearly two years, on January 11, 2023, Plaintiff injured himself while attempting to fill the air rifle with compressed air. He sustained an injury to his left thumb.

Defendants Texas Machine Parts, Danny Duke, and John Wiley filed a motion to exclude Plaintiff’s experts, Kennith Comeaux and William Caster, or, in the alternative, to exclude any testimony from them related to medical causation.

Firearms Expert Witness

Kennith R. Comeaux has thirty-five years of experience as a gunsmith. Because of his familiarity with guns, in his other career as a certified ISO 9000 quality auditor, he “was allowed to audit firearms manufacturers and ammunition manufacturers” to determine if the companies could get ISO certified by meeting “an international standard associated with quality that is very similar to OSHA with respect to safety, but for quality.”

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Air Mechanics Expert Witness

William B. Caster, Jr. holds a certification from the National Balancing Council, “a group that educates and teaches in air balancing and hydronic balancing, which is airflow CFM delivery, pressure, and velocity.” He owns a consulting company for heating, ventilation and air conditioning, airflow dynamics, hydronic testing, and air testing.

Want to know more about the challenges William Caster has faced? Get the full details with our Challenge Study report.

Discussion by the Court

A. Kennith Comeaux

Though Comeaux acknowledged that he is not an expert in gun manufacturing, his experience in being able to quality-audit firearms and ammunition manufacturers underscores his gunsmithing experience.

Comeaux also relied on sufficient facts and data to reach his conclusions and utilized reliable principals and methods. Importantly, he personally inspected the air rifle as well as consulted an American Society for Testing and Materials (ASTM) manual, looked at the subject air rifle’s owner’s manual as well as the owner’s manuals of other similar rifles, and researched other manufacturer’s diagrams.

Comeaux also explained his methodology and how it comports with the ASTM and could be replicated by others. His decades-long experience as a gunsmith, combined with the foregoing, allowed the Court to find that Comeaux’s testimony is sufficiently reliable.

It is also clear that Comeaux’s testimony will assist the trier of fact and is relevant. For example, one line of Comeaux’s report reads: “Further attempts to seat the exhaust valve without removal of the air chamber cap were unsuccessful including lubrication with Teflon oil.” This shows that Comeaux will provide testimony that goes beyond “common sense.”

Moreover, this sort of testimony is relevant because Plaintiff’s claims are based in the alleged faulty function and design of the valves in the subject air rifle and a replacement valve assembly, and Comeaux’s testimony reflects his personal evaluation of the air rifle and its replacement valve.

B. William Caster

Caster’s testimony is based on sufficient facts and data. Like Comeaux, Caster personally inspected the air rifle at issue.

He conducted research on the relevant parts included in his testing. Moreover, he limited his testing to his discipline, explaining that he did not operate or fill the air rifle during his testing because he “went there to find out if the equipment that [Plaintiff] utilized for filling the gun exceeded the capabilities or burst pressure of the gun.” As to reliable principles and methods, Caster did not conduct explicit testing like Comeaux, but rather researched and observed whether Plaintiff possessed the “tooling to be able to” fill the air rifle’s air tank beyond its PSI specifications. Caster explained that he based his conclusions off “the actual flow chart of the gun from the tank to the valve to the barrel” because “the only point of when air can enter into the chamber is when the valve is released.”

Considering these circumstances, the Court found that Caster is qualified to testify at trial based on his experience and the nature and formulation of his opinions.

C. Medical Causation Testimony

Defendants asked that both Comeaux and Caster be excluded from offering medical causation testimony because they are not medical doctors.

To the extent either expert anticipates opining on medical causation at the trial of this matter, the Court will foreclose them from offering any such testimony. Neither Comeaux nor Caster are medical doctors.

Held

The Court denied Defendants’ motion in limine to exclude the testimony of Kennith Comeaux and William Caster.

Key Takeaway

The fact that opposing parties do not agree with the facts relied upon by the experts or their interpretation of those facts does not render their opinions irrelevant or unreliable; challenges related to the basis of any of the experts’ opinions are thus best suited for cross-examination, not exclusion.

Case Details:

Case Caption:	Cornwell V. Extreme Tactical Components, LLC
Docket Number:	2:24cv926
Court Name:	United States District Court, Louisiana Eastern
Order Date:	January 15, 2026

Category: Air Mechanics Expert Witness

Firearms Expert Allowed to Opine on Air Rifle

Firearms Expert Allowed to Opine on Air Rifle