The Component Parts Doctrine in Massachusetts Product Liability Cases

A recent Appeals Court case affirms that in a Massachusetts Product Liability Case, as a general rule, the manufacturer of a non-defective component part has no duty to warn of risks posed by the assembled product that arise out of the addition of other components and the decisions made, and actions taken, by downstream actors, even where the manufacturer designed and provided an incomplete product intended to be modified and even though the dangers raised by use of the finished product may have been foreseeable. The rule, known as the “component parts doctrine,” identifies a clear line limiting the liability of a component part manufacturer to cases where a component part itself is defective and causes damage.

Case Study: Component Part Manufacturer Liability

In the Appeals Court case, a widow brought a wrongful death suit against a truck manufacturer and the manufacturer of an auxiliary power system used to transform the incomplete truck purchased by her husband into a dump truck. The widow alleged that her husband was killed when his clothing caught up in a spinning universal joint that was part of the mechanical system added and used to tilt the dump body of the truck. She further contended that the truck and power system manufacturers had a duty to warn of the foreseeable and serious potential dangers to someone working underneath the truck while the system was engaged. She did not allege that any of the individual component parts were defective, but rather that the completed product was dangerous as assembled, and that it was foreseeable that the truck would be assembled as it was, such that the component manufacturers had a duty to warn installers and end users about the dangers posed by the unguarded auxiliary drive shaft and U-joints. It was uncontested that the system could have been installed in a manner that alleviated the risks that caused the husband’s death. However, it was not known who performed the outfitting of the incomplete vehicle.

In affirming summary judgment for the component manufacturers, the Appeals Court, reasoned that product components can be put to different uses depending on how they are integrated into other products and a seller is ordinarily not liable for failing to incorporate a safety feature that is peculiar to a specific adaptation. A safety feature important for one adaptation may be wholly unnecessary or inappropriate for a different adaptation. The court noted that the incomplete vehicle purchased in the case could have been outfitted for everything from a flatbed truck to a fire truck. In addition, the court found that foreseeability itself was insufficient to create a legal duty on the part of the component manufacturers where the state’s highest court had previously determined that the manufacturer of a non-defective component part has no underlying duty to warn of risks posed by the assembled product. The court concluded that whoever assembled the auxiliary drive system might well have faced a duty to warn future truck users of the dangers that system posed, and the fact that such parties could not be identified in the case did not provide a valid reason for rendering upstream component parts manufacturers liable.


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