Products Liability Law Daily Injured circular saw user unable to proceed without admissible expert evidence of defect, causation
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Wednesday, November 6, 2019

Injured circular saw user unable to proceed without admissible expert evidence of defect, causation

By David Yucht, J.D.

The user’s expert failed to test his opinions and did not offer an alternative design for the allegedly defective saw on which the user cut his hand.

Summary judgment favoring the manufacturer and the retailer of a circular saw was warranted in an action by a user who claimed that he had been injured by the product, a Missouri federal court ruled, finding that a mechanical engineer hired as an expert witness by the user failed to support any of his opinions concerning the proximate cause of the accident or the defective nature of the saw at issue. Consequently, the court barred the user from offering the expert’s opinions at trial, without which the user had insufficient evidence to support his claims (McMahon v. Robert Bosch Tool Corp., November 5, 2019, Clark, S.).

An individual suffered injuries to his hand when the auxiliary handle of a RotoZip Model RZ20 hand-held spiral saw detached from the body of the saw while he was using it, causing him to drop the saw while the blade was still in motion. The saw was manufactured by Robert Bosch Tool Corporation (Bosch) and sold by Lowe’s Home Centers, LLC. At the time of the accident, the user was holding the saw with one hand and was using a wood carving blade with deep grooved teeth in the saw’s "Zipmate" attachment, even though the saw’s user manual expressly warned against using wood cutting toothed blades with that attachment and against holding the saw with just one hand. To detach the auxiliary, a user needed to slide a lock pin to either side and, while holding the lock pin, depress a separate handle release button. The user in the case at bar testified that the handle detached despite his not having pressed the handle-release button.

Following the accident, the user noticed that the part of the latching mechanism that holds the auxiliary handle to the saw was damaged in that a portion of a plastic receptacle shelf was broken off. The user testified that he inspected the saw before the accident and did not observe any damage to this mechanism. He also testified that he would not have used the saw if he had seen any such damage because the handle could come loose.

Complaint and expert opinion. The user’s complaint asserted claims against both Bosch and Lowe’s under theories of strict and negligent products liability for design defect, negligent failure to warn, and negligent supply of a dangerous instrumentality. The user retained a mechanical engineer as an expert witness to testify concerning defects in the saw’s design. The expert opined that the handle connections on the saw were defective and caused the release of the saw. He also opined that the handle connection design was defective, and that the handle’s failure was highly foreseeable because: (1) the connection method on the movable latch invited wear; (2) wear and tear reduced the holding force available; and (3) the two-factor locking scheme was reduced to a one-factor locking scheme in some cases. In addition, the expert opined that the handle-release button’s placement was defective because it promoted user thumb placement on the button, and the saw should have had an interlock device to stop the motor once the auxiliary handle detached.

Bosch and Lowe’s moved to exclude these opinions and for summary judgment.

Expert testimony. The trial court barred the user’s mechanical engineer from testifying. The engineer did not conduct testing to establish that the saw was in an unreasonably dangerous condition at the time of its manufacture and sale. He did not examine any exemplar saws. He did not test how the latch mechanism’s receptacle shelf broke, and he conceded that he would have to speculate as to what caused it to break. Moreover, he conducted no testing to establish that the saw’s handle design caused the receptacle shelf to break and he failed to test to determine if the receptacle shelf broke when the tool fell during the accident. He did not conduct any testing to rule out other potential causes of the accident such as the use of a wood carving blade in the saw. His theories had not been scrutinized by the scientific community and he did not cite any peer-reviewed articles or other authorities. The court concluded that these opinions were connected to existing data only by the say so of the expert and, consequently, were inadmissible.

The court also concluded that the expert’s alternative design opinions were unreliable. It found that the expert had not shown a factual basis to support his opinion that proposed modifications were feasible or that they would not interfere with the saw’s utility, or that they would have prevented the accident. He failed to adequately develop his theories, which essentially were mere ideas or conceptualizations. He did not prepare any alternative designs, nor did he point to other manufacturers whose existing products incorporated the safety features he described. As for alternative warnings, the expert agreed that the saw’s user manual warned against using the type of blade that the user was using at the time of the accident, and he had prepared no alternative warnings.

After finding the expert’s opinions to be "speculative and so fundamentally unsupported" that they could not offer assistance to the jury, the court excluded them.

Summary judgment. Without expert testimony, the user could not prove that inadequate warnings had been the cause of his injuries, and so his failure to warn claim was dismissed. Moreover, he had no evidence that a defect in the saw was the proximate cause of his injuries. Consequently, the court granted summary judgment and dismissed the user’s claims.

The case is No. 4:18-cv-00583-SRC.

Attorneys: Shaun M. Falvey (Goldblatt + Singer) for Jeffrey McMahon. J. Phillip Bryant (Pitzer Snodgrass, P.C.) and Joseph Paul Switzer (Swanson and Martin, LLP) for Robert Bosch Tool Corp. and Lowe's Home Centers, LLC.

Companies: Robert Bosch Tool Corp.; Lowe’s Home Centers, LLC

MainStory: TopStory DesignManufacturingNews WarningsNews CausationNews ExpertEvidenceNews ToolsHardwareNews MissouriNews

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