Mechanical Engineering Expert Not Allowed to Opine on the Saw's Design Flaws

In 2011, Plaintiff worked for a car dealership. The dealership hired a contractor to do renovation work. In connection with his work, in 2011, the contractor bought a ten-inch Ryobi table saw, model number BTS10S ("Saw"), from Home Depot. After his work ended, the contractor left the Saw at the dealership.

In March or April 2019, the dealership told Plaintiff to take the Saw. At first, Plaintiff "didn't want to" because he thought it was "a piece of junk." Plaintiff thought the Saw was a "piece of junk" because he observed the contractor "struggle to get a good cut" with the Saw. Nevertheless, Plaintiff took and used the Saw.

On June 22, 2019, Plaintiff began cutting a piece of wood with the Saw. About "four inches into the cut," the cut became "violently rough," and the Saw began "shaking." In less than a second, Plaintiff's left hand struck the Saw's blade, severing his thumb and index finger.

Plaintiff eventually sued Defendants for product liability and breach of express warranty. Plaintiff identified Arthur Coons as his liability expert. Coons is a professional engineer who does woodworking as a hobby. After disassembling, examining, and testing the Saw, Coons asserted the Saw had two defects. First, Coons opined the Saw's table was too small, leaving Plaintiff's fingers too close to the blade. Second, Coons asserted the Saw's blade adjustment height mechanism was defective because "the gap between the washer and the mounting plate . . . was improperly adjusted during assembly at the factory."

After learning Coons disassembled the Saw, Defendants moved to strike his testimony in March 2025, arguing the disassembly constituted spoliation and fraudulent concealment. The Court denied the motion without prejudice in October 2025, as Defendants did not show Coons acted in bad faith. However, the Court granted Defendants leave to depose Coons and file a renewed motion to strike. In November 2025, Defendants deposed Coons. After the deposition, Plaintiff sought "leave to seek a new expert witness to replace Coons due to . . . his deteriorated mental state." The Court denied Plaintiff's motion for leave to identify a new liability expert, finding that, "to now repudiate Coons as his expert witness and replace him with another, based on no more than unsubstantiated assertions about Coons's purported impairments, Plaintiff would not only restart expert discovery, at a substantial cost to Defendants, but also place Defendants at significant tactical disadvantage."

On September 1, 2026—over four months after Defendants moved for summary judgment—Plaintiff requested the Court allow him to use Coons as an expert. The parties have submitted briefs as to the admissibility of Coons' testimony. On October 7, 2026, the Court heard oral argument on the issue. These matters are now fully briefed and ripe for a decision.

Mechanical Engineering Expert Witness

Arthur G. Coons, PE, is a licensed Professional Engineer registered in the State of New York and has been a licensed engineer for more than 45 years. He began his education at Columbia University in New York City, initially studying structural engineering, before changing his major to mechanical engineering with a specialization in machine design and advanced stress analysis, specifically Finite Element Analysis (FEA). He completed his studies with a Master’s Degree in Mechanical Engineering from Union College.

Coons’ professional career has centered on designing, building, and installing industrial machinery.

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Discussion by the Court

A. The Court Grants Plaintiff's Request to Reinstate Coons

Evidentiary rulings, "including the decision to admit or exclude expert testimony," are committed to the Court's discretion. The first issue before the Court involves Plaintiff's request to reinstate Coons as his expert. Plaintiff identified Coons as a liability expert, withdrew Coons as an expert, and again seeks to use Coons as an expert.

Properly framed, the question is whether Plaintiff, due to his own conduct, must proceed without the expert he previously identified. After considering the relative prejudice to the parties, fairness, and the preference for resolving cases on the merits, the Court will grant Plaintiff's request. In terms of prejudice, the Court noted Plaintiff inexcusably waited until after Defendants moved for summary judgment to reinstate Coons.

That said, the choice before the Court is not between Coons and a new expert; rather, Coons and no expert. Barring Plaintiff, a pro se litigant, from using his only expert based on his own conduct is a potentially case-ending sanction, preventing a full decision on the merits. Granting Plaintiff's request, on the other hand, only minimally prejudices Defendants. Doing so will not require Defendants to file a Daubert motion (as the Court raised the issue sua sponte) or a new summary judgment motion (as the Court will consider Defendants' existing motion as filed). Therefore, the Court granted Plaintiff's request to reinstate Coons.

B. The Court Excludes Coons' Testimony

Though the Court does not bar Coons due to Plaintiff's conduct, the Court must still determine whether Coons' testimony is admissible. Those are separate questions, as the Court has a "basic gatekeeping obligation" to ensure "all expert testimony" is relevant and reliable.

i. Coons is Unqualified as a Liability Expert

Coons asserted the Saw had design and manufacturing defects. Yet Coons has never designed a table saw; worked with or consulted for a table saw designer or manufacturer; been inside a table saw factory; set any safety standards for table saws; read any safety standards for table saws; or reconstructed a table saw accident. Coons' sole experience comes from recreational woodworking and once teaching seventh-graders how to use a table saw in 1977. But the fact that Coons knows how to use a table saw does not mean he knows how to design, manufacture, or reconstruct an accident involving one.

Moreover, Coons' professional engineering experience—in which he investigated catastrophic failures of very large industrial machines, not table saws—has "nothing to do with the questions" Coons must address: "whether the Saw was defective because it could have been designed, without compromising its effectiveness or unreasonably increasing its cost, with certain safety features"; whether, when it rolled off the assembly line, the Saw deviated from the manufacturer's standards; and "whether those 'defects' caused [Plaintiff's] injuries."

Accordingly, the Court held that Coons is unqualified to offer an expert opinion about the design or manufacture of the Saw or the cause of the accident.

ii. Coons' Liability Opinions are Unreliable

Here, Coons based his opinions about the Saw's design flaws entirely on his own experience and intuition. Further, Coons did not perform any testing "to inform his criticism of the Saw's design or to substantiate his design proposals." This alone is "fatal for his designation as an expert."

Moreover, Coons acknowledged he never reviewed "any specifications" for manufacturing the Saw and did not know the manufacturer's intended distance between the washer and mounting plate. Nor did Coons consider (a) whether the accident could not have occurred "at this point" in the Saw's lifespan, had there been no manufacturing defect, (b) any other possible causes of the Saw's failure, or (c) whether the accident was not "solely the result of causes other than" the Saw's alleged manufacturing defect.

Instead, Coons simply assumed the manufacturer placed the washer and mounting plate too far apart, which must have caused the accident. But this is precisely the kind of "haphazard, intuitive inquiry" the Court must exclude.

Finally, Coons did not reliably reconstruct the accident. Coons hypothesizes that (a) based on his own woodworking experience, Plaintiff's injury sounded like a kickback accident, particularly because, in his estimation, Plaintiff had "very good" machine handling skills; (b) kickback can occur when power is drawn away from a table saw; (c) a large air conditioner could draw power away from a table saw; and (d) Plaintiff had a very large air conditioning unit.

Therefore, Coons determined, Plaintiff's air conditioning unit came online while he was using the Saw, causing kickback. But the Coons Report offered no reference to material, publication, or literature describing the failure scenario he presented.

To bridge the significant analytical gap between Coons' data and his opinions, Coons relies on his own expertise and intuition rather than any evidence. Accordingly, his accident reconstruction opinion is unreliable.

iii. Coons' Testimony Does Not Fit the Proceedings

Coons did not give the "why" or "wherefore" underlying his opinions. Coons simply asserts the Saw "was at fault for the incident . . . due to not having enough table area to manually position work material into the blade for a rip cut." He never explains why a larger table would have prevented the accident, or whether such a change would be feasible or effective. Similarly, Coons concludes the blade height adjustment unit "was improperly adjusted during assembly at the factory" without identifying any basis for his opinion. Moreover, Coons offers no independent analysis for how the accident occurred. He simply accepts Plaintiff's version of events. That is of no assistance to the factfinder.

Because Coons is not qualified to testify about table saw design, table saw manufacture, or accident reconstruction, his opinions are unreliable, and they would not assist the factfinder; the Court excluded his testimony.

Held

The Court excluded the testimony of Arthur G. Coons.

Key Takeaway

An expert's bare conclusions are not admissible under the fit requirement of Rule 702 of the Federal Rules of Evidence. Rather, an expert must give the "why and wherefore" underlying their opinion.

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