Expert Testimony Curtailed in Defective Conveyor Case
Posted on July 29, 2025 by Expert Witness Profiler
In July 2022, while working at Tyoga Container Company’s facility, William Borden stepped onto a mesh belt conveyor manufactured by Mainline Conveyor System, Inc. The conveyor unexpectedly activated and threw him off, causing severe lacerations to his left knee and lower leg. Borden claimed that the conveyor was defective and unreasonably dangerous.
In August 2023, Borden filed a strict liability lawsuit against Mainline in the Pennsylvania Court of Common Pleas of Tioga County. The following month, Mainline removed the case to federal court on diversity grounds.
Borden sought to exclude testimony from Mainline’s engineering expert, George J. Wharton; evidence suggesting product misuse or highly reckless conduct; evidence of assumption of risk; and evidence of his prior DUI conviction.
Safety Engineering Expert Witness
George J. Wharton is a professional engineer with multiple certifications, including C.F.E.I., C.V.F.I., and C.F.P.S., and holds both B.S. and M.S. degrees in mechanical engineering. Wharton serves as an expert in engineering, safety engineering, and personal injury matters.
His work includes evaluating mechanical system design, workplace safety procedures, and incident causation. Wharton has also authored expert reports responding to opposing experts’ claims and opining on industry practices based on decades of engineering experience.
Discussion by the Court
Contract Interpretation
Wharton’s opinion that Tyoga was “required” to assume safety responsibilities under its contract with Mainline crossed into legal interpretation. Since his conclusion relied on contract language rather than engineering practices, the court deemed it inadmissible.
Design vs. Knowledge
Wharton did not offer an opinion on Mainline’s subjective knowledge. Instead, he responded to the opposing expert’s foreseeability claim by analyzing the design differences between conveyors. This design-focused rebuttal was found admissible.
Speculation on Plaintiff’s Behavior
Wharton asserted that a warning decal wouldn’t have influenced Borden’s decision to cross the conveyor. This opinion was based on speculation about Borden’s mindset and was therefore excluded as outside the scope of expert testimony.
Alarm System Commentary
Wharton’s critique of an audio-visual alarm system addressed practical feasibility—highlighting how excessive alarms could lead to desensitization or muting. Grounded in engineering experience, this testimony was allowed.
Post-Accident Procedures
The Court excluded any opinion referencing Tyoga’s post-accident policies, including a sign in Wharton’s report, under the parties’ pretrial agreement.
Held
The Court granted in part and denied in part Plaintiff Borden’s motion to exclude the testimony of Defendant Mainline’s expert witness, George J. Wharton.
Key Takeaway:
An engineering expert may testify about industry practices, product design, and the feasibility of safety features, but cannot interpret contractual obligations or speculate on a party’s mental state or motivations. Courts will exclude expert opinions that cross into legal conclusions or subjective speculation.
Case Details:
| Case Caption: | Borden v. Mainline Conveyor Sys., Inc |
| Docket Number: | 4:23cv01486 |
| Court Name: | United States District Court for the Middle District of Pennsylvania |
| Order Date: | July 21, 2025 |
