Intellectual Property Expert’s Opinion as to a Safer Design for a Splitting Maul Admitted
Posted on April 25, 2025 by Expert Witness Profiler
Plaintiff, Joseph Ferlito purchased a splitting maul (an axe specially designed for splitting wood) from Defendant, Harbor Freight Tools USA, Inc. in 2017. Several months later, while the Plaintiff was hanging the maul to store it, the head of the tool detached and struck Plaintiff, causing injuries to his nose and left eye. Plaintiff initiated this product liability lawsuit in 2020, alleging that the head detached due to a design defect.
To support his defective design claim, Plaintiff sought to offer expert testimony by Mark Lehnert, who identifies himself as a “consultant with products and liability history, extensive knowledge and experience in manufacturing and assembly, [and] mechanical and electrical engineering management.”
Defendant filed a motion to preclude Lehnert’s testimony, arguing that he is unqualified as an expert because he lacks engineering degrees, and his experience is limited to designing power tools rather than manual tools. Moreover, the Defendant contended that Lehnert’s opinion is unreliable because (i) he did not rely on any scientific, technical, or trade articles in preparing his report, and (ii) after completing the report, he entered a query into ChatGPT about the best way to secure a hammer head to a handle, which produced a response consistent with his expert opinion.
Intellectual Property Expert Witness
Mark Lehnert is an independent consultant with P&L history, extensive knowledge and experience in M&A, mechanical and electrical engineering management, and Intellectual Property processes. He is currently certified by the Supreme Court in Florida as a Mediator and Arbitrator in the 5th District.
Discussion by the Court
Lehnert’s Qualifications
The Court held that Lehnert met the modest standards to qualify as an expert. Based on Lehnert’s experience designing products and supervising engineering teams, his opinion as to a safer design for a splitting maul will likely be helpful to a jury of laypeople. Lehnert’s lack of engineering degrees or professional licenses did not necessitate exclusion of his testimony; opposing counsel can address on cross-examination. Furthermore, the fact that Lehnert’s professional experience is limited to power tools did not preclude his testimony here.
Reliability of Lehnert’s Testimony
Initially, Lehnert’s report focuses almost exclusively on potential flaws in the design of Defendant’s maul and proposes an alternative design—specifically, incorporating a metal pin to better secure the maul’s head to its handle—that he asserted would be safer and cost-effective.
Although Lehnert conceded he did not test his proposed design, he identified existing products, including other splitting mauls, that use such a pin, meaning that, testing is not required to establish the reliability of Lehnert’s testimony.
Finally, the fact that Lehnert did not rely on any peer-reviewed articles in preparing his report is appropriately addressed via cross-examination rather than by exclusion.
As a result, the Court determined that Lehnert’s proposed testimony satisfied the reliability standard.
Lehnert’s Use of ChatGPT
There is little risk that Lehnert’s use of ChatGPT impaired his judgment regarding proper methods for securing the maul’s head to its handle. The record from the hearing reflects that Lehnert used ChatGPT after he had written his report to confirm his findings, which were based on his decades of experience joining dissimilar materials.
Since there is no indication that Lehnert used ChatGPT to generate a report with false authority or that his testimony’s reliability was diminished by AI, the Court finds no issue with his use of it here.
Use of Hyperbole
Defense counsel raised concerns at the hearing regarding Lehnert’s apparent inclination towards hyperbole, a view the Court is inclined to accept. Several instances occurred where Lehnert presented information in an overly broad manner, raising questions about its precision. Although these verbal embellishments, in themselves, do not warrant exclusion of the witness’s testimony, the Court advised Plaintiff’s counsel to ensure Lehnert is instructed to refrain from exaggeration when presenting his testimony to the jury.
Held
The Court denied Defendant’s motion to exclude Plaintiff’s expert witness, Mark Lehnert.
Key Takeaway:
The Court emphasized that experts can use “AI for research purposes” given its “potential to revolutionize legal practice for the better.” Daubert issues arise only “when attorneys and experts abdicate their independent judgment and critical thinking skills in favor of ready-made AI-generated answers.”
Case Details:
| Case Caption: | Ferlito V. Harbor Freight Tools USA, Inc. |
| Docket Number: | 2:20cv5615 |
| Court Name: | United States District Court, New York Eastern |
| Order Date: | April 23, 2025 |
