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Defenses to Product Liability Actions- Module 5 of 5

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Module 5: Defenses to Product Liability Actions


Under product liability law, product manufacturers and sellers are expected to distribute safe and reliable products. When they fail to do so, and the users of these products are harmed, parties in the chain of distribution can be held liable for damages. The burden of responsibility for defective products is on manufacturers and sellers who distribute the products rather than on those who purchase them. This is because those involved in manufacturing and distribution are in a better position to know and control its quality and danger.

However, this rule of liability is not absolute. When users of defective products act in a way that makes the product more dangerous than it was at time of sale, the law will sometimes hold the user responsible for his or her own injuries. So, the conduct of the plaintiff, as well as other considerations, can provide a variety of defenses for the defendant in a products liability case. Some of the defenses are based on general common law principles applicable to other torts, while others are statutory defenses which apply specifically to products liability cases.

Contributory Negligence of the User

Manufacturers are liable for producing and selling products that are defective and may cause harm to users. However, under general tort law principles, a plaintiff who acts negligently and contributes to his or her own harm may be limited in the ability to recover. In the past, courts have been reluctant to permit defendants to use plaintiff’s negligence as a defense in product liability cases, since product liability concerns the quality of a product rather than the conduct of the defendant.[1]

However, contemporary decisions have held that when a user suffers an injury from a defective product due in part to his or her own negligent conduct, this may reduce or eliminate the liability of the manufacturer.[2] This defense has been recognized by most jurisdictions in situations in which the plaintiff’s conduct combines with the product defect to cause injury.[3]

One case in which the plaintiff’s negligence was deemed sufficient to serve as a defense to products liability involved a pickup truck that rolled backwards and struck the driver who had gotten out of the truck. The court found that the truck was designed defectively, and that the manufacturer did not include adequate warning of foreseeable dangers. However, the damages awarded to the estate of the victim were reduced by half because the jury found that the plaintiff was negligent in leaving the truck without first properly parking it.[4] This failure to use ordinary care served as a partial defense even though the truck was defective, and this defect led to the harm.

The standard for how much the plaintiff’s negligence may reduce an award depends on the jurisdiction.[5] The way a jurisdiction treats contributory negligence in general torts cases will usually be applied in product liability cases as well.  

Defining negligence in product liability cases

The rule of comparative negligence reduces or eliminates the defendant’s liability when a plaintiff fails to meet a standard of reasonable care, and the lack of care is a proximate cause of the injury. This standard includes conduct that would be high risk even without the defect, which combines with the defect to create harm, or make it worse. For example, in one case a plaintiff was thrown from his car due to a defect in the door latch, but was also intoxicated, and had failed to use the seatbelt or lock the car door.[6]

Certain types of plaintiff negligence are particularly pertinent for products liability cases. For example, many commercial products are manufactured with specially designed safety features that protect the user. A failure on the part of the purchaser to employ these safety features can be considered a form of negligence and will reduce the potential damages award. The decision not to use a seatbelt while in a moving car is one example of a failure to use a product with the proper safety equipment provided by the manufacturer.[7]


Still, even when a plaintiff acts carelessly, the burden for discovering and eliminating defects remains with the manufacturer. So, a failure on the part of the user to discover the defect will generally not be considered user negligence.[8]

Assumption of Risk


A similar defense against products liability claims come from the doctrine of assumption of the risk. In tort law, the victim of an injury is said to assume the risk of harm by knowingly engaging in behavior that carries with it risk of injury. Assumption of risk serves a defense to a tort claim if the plaintiff knew and understood the risks of the behavior and chose to engage in the behavior anyway.[9]


In product liability cases, a victim of a product defect has assumed the risk of harm if he or she knows the nature of the product defect, and unreasonably decides to use the product in its defective condition.[10] To illustrate, consider the case of someone who was severely injured after the steering wheel in his pickup truck locked in place, leading to a serious accident.


In this real-life case, the defendant cited the driver’s own admission that this problem with the steering wheel had occurred before, and the driver continued to drive the truck, knowing that the defect made it unsafe to drive. The court agreed that such knowing disregard of a product defect would constitute an assumption of the risk on the part of the victim, and would bar him from recovery.[11]


Note, however, that assumption of risk does not protect the defendant from all possible injuries. If the plaintiff uses a product despite being aware of a dangerous defect, but is injured by another, unknown defect, there is no bar on recovery for that other injury.


Finally, in most jurisdictions, assumption of risk in product liability cases is treated like comparative negligence, in which damage awards are reduced in proportion to the degree of fault of the plaintiff. Only in a minority of jurisdictions is assumption of risk a complete defense.[12]




The general rule governing product liability is that a seller is required to provide products for sale that are not unreasonably dangerous when used in an expected and foreseeable manner. If a product is unreasonably dangerous when used in a common and foreseeable way, it is considered defective.


Therefore, one avenue open to a defendant in a product liability case is to argue that the harm suffered by the plaintiff was a result of using the product in an unexpected and unforeseeable way. Thus, misuse can serve as a defense against liability. The misuse, however, must be unforeseeable. If the seller has reason to know that the product would be used in a manner for which it may not be designed, misuse may not suffice to free the manufacturer from liability.[13] For example, while solid wooden chairs may be made for sitting on and not standing on, it may certainly be foreseeable that customers would use the chairs to stand on to change light bulbs. That the customer is not using the chair precisely for its intended use may not preclude liability.


To demonstrate how the law treats user misuse and the question of foreseeability, it will be useful to contrast two types of circumstances. Many product liability cases involve motor vehicle accidents. Such accidents are usually the result of driver error or may be nobody’s fault at all. Since such accidents are common, and the consequences can be extremely severe, the law generally considers car collisions to be instances of foreseeable misuse of a product. While cars are not intended to be used in a way that involves collisions, the law requires car manufacturers to design cars to be reasonably safe even when such collisions occur.[14] This is known as the crashworthiness doctrine.


So, car manufacturers are required to take steps to mitigate injuries in cases of motor vehicle collisions, since such collisions are to be expected even though not intended. In practice, this means designing vehicles with features that protect occupants from preventable injury in cases of car crashes, such as by installing airbags and head restraints, employing safety cages or crumple zones, and durable car roofs to prevent collapse if the car rolls over.


At the other end of the spectrum, are cases in which the misuse of a product is completely unforeseeable, and so the manufacturer has no obligation to consider the risks of such misuses when designing the product.


Following the 1993 bombing of the World Trade Center in New York, a lawsuit was brought against the manufacturer of the fertilizer that had been used to create the explosive device used in the attack. The plaintiff argued that the fertilizer could have been produced in a way that would have made it impossible to use it as an ingredient in an explosive device, and that the failure to do so constituted a design defect. However, the court ruled that such a use of fertilizer, which in and of itself poses no danger, was not reasonably foreseeable. As such, it would be grossly unfair to impose a duty on the defendant to anticipate and design their product in a way that would prevent its misuse as part of an explosive device.[15]


Substantial Modification


Liability for defective products attaches to manufacturers when the product in question reaches the user or the consumer without substantial change from the condition in which it was sold.[16] If a product is substantially altered from its original condition in such a way as to render it unsafe, the manufacturer will not be responsible for injuries resulting from the modification.[17]


The most common form of modification that absolves the manufacturer of liability is the removal of safety devices designed to make the product safe for use. This was the situation in a case involving an employee at a meat factory whose hand was severely injured when she used an industrial blender with the safety guard removed. Since the purpose of the guard was to prevent the specific kind of injury the employee suffered, the removal of the guard was deemed to be a substantial modification of the blender, and the manufacturer was absolved of liability.[18]


Note, however, that modification of the product is not a blanket defense for a manufacturer. Courts have held that if the modification is reasonably foreseeable, the manufacturer may still be liable for selling a product that would be unreasonably dangerous if its removable safety device is removed. In fact, the dissent in the meat factory case argued that, since the blender was operable without the safety feature, as well as the fact that the safety feature was shipped separately from the device, and the manufacturer included warnings against removal, these could all be evidence that such removal was in fact foreseeable. This would mean that the manufacturer would be liable despite the substantial modification.[19] While that argument did not prevail in that case, it illustrates how these cases can be determined on a case-by-case basis.


The law treats foreseeable modification in the same way as foreseeable misuse. In both cases, the burden on the manufacturer is to distribute a product that is safe for foreseeable conduct by the product users.


Federal Preemption

Under the rule of preemption, the legal standards and regulatory schemes enacted in a state legislature are displaced in favor of federal regulations for a specific area of law. The preemption doctrine is rooted in the Supremacy Clause of the US Constitution, which establishes the supremacy of the federal government over state governments as a legal authority. This means that, in some spheres of law for which the federal government enacts substantive legislation, state rules and regulation are preempted in favor of federal standards. When federal preemption is applicable, state laws that hold product manufacturers liable will give way to federal law. This opens the way for a defendant in a products liability case to assert that state laws, which may be more demanding on manufacturers, are inapplicable due to federal preemption.

The preempting of state laws in favor of federal law may be expressly stated in federal legislation. For example, the federal statute requiring labels on cigarette packages warning of the dangers of smoking also explicitly states that no other form of warning, aside from what is federally mandated, is required.[20] As a result, product liability cases based on the failure of manufacturers to provide adequate warnings regarding the risks of cigarette smoking are preempted by the federal standards.[21]

There are also other areas of product liability in which the scope of legal claims is limited due to the implied preemption of state law in a specific area. One such area concerns the liability of manufacturers for failing to include driver side airbags in cars. Court have rejected the claim that failure to design a car with an airbag constitutes a design defect, because federal law did not mandate that all cars have airbags. The rationale was that Congress deliberately rejected a universal airbag requirement out of concerns related to cost, as well as concerns as to how airbags would impact the use of seatbelts. Therefore, a state law that required airbags would conflict with the terms and the goals of the federal statute.[22]

Courts have applied the preemption doctrine even without direct conflict between state and federal law when it is evident that the federal government intends to occupy a distinct field of regulation. Courts infer from federal actions and legislation that the federal government aims to be the sole regulator of an area of regulation. A strong indicator of preemption based on occupation of an entire field is when there is an evident need for uniform rules across the nation, which would be impeded by divergent state rules.

One such area is the regulation of railroad locomotives. Federal regulations have long mandated that railroad carriers may only allow a locomotive to run on their lines if the locomotives meet federal standards and comply with regulations set by designated federal officials.[23] The Supreme Court inferred from successive pieces of legislation that the federal government was acting to establish a uniform national standard for railroad locomotive safety. This means that no product liability claims can be brought at the state level in the field of locomotive equipment, regardless of whether there is any conflict between state and federal laws.[24]

Another area of products liability law in which federal preemption arises concerns the regulation of prescription drugs and medical devices. The rationale has been that by passing the Food and Drug Act, a law that organizes a federal agency (the Food and Drug Administration) to regulate the safety and quality of medical devices and prescriptions drugs, the federal government was signaling that regulation in this area was to be entrusted solely to the expert federal agency.[25]


            Thank for you listening to our course on product liability. Product liability is a high-stakes area of tort law that gives rise to many large judgments. It is broken down to actions on four theories: manufacturing defects, design defects, failure to warn and breach of warranty. As we have seen, each theory comes with its own set of standards and potential defenses. Best of luck and please contact us with any questions or feedback.


[1] Restatement(2nd) of Torts §402A comment n.

[2] Epstein, Torts, §16.15, p. 430 (Aspen Publishers, 1st Ed. 1999).

[4] General Motors Corp. v. Sanchez, 997 S.W.2d 584 (Tex. 1999).

[5] Restatement (3rd) of Torts: Prods Liab., §17(a).

[6] Daly v. General Motors Corp. 575 P.2d 1162, 20 Cal. 3d 725, 144 Cal. Rptr. 380 (1978).

[7] See Daly v. General Motors Corp., 575 P.2d 1162 (1978).

[8] Restatement (3rd) of Torts: Prods Liab., §17 comment d.

[9] See PROSSER & KEETON ON TORTS, § 68, p. 486-87.

[10] Restatement (2nd) of Torts §402A comment n.

[11] Ferraro v. Ford Motor Co., 423 Pa. 324, 223 A.2d 746 (1966).

[12] Restatement (3rd) of Torts: Prods Liab., §17 comment a.

[13] Binakonsky v. Ford Motor Co., 133 F.3d 281 (4th Cir. 1998).

[14] See Larsen v. General Motors Corporation, 391 F.2d 495 (8th Cir. 1968).

[15] PORT AUTHORITY OF NY AND NJ v. Arcadian Corp., 189 F.3d 305 (3d Cir. 1999).

[16] Rest 2nd 402A(b)

[17] Robinson v. Reed-Prentice, 49 N.Y.2d 471, 403 N.E.2d 440 (1980).

[18] Davis v. Berwind Corp., 690 A.2d 186, 547 Pa. 260 (1997).

[19] Davis v. Berwind Corp., 690 A.2d 186, 547 Pa. 260 (1997).

[20] 15 U.S.C. ch. 36 § 1331 et seq.

[21] Cipollonev. Liggett Group, Inc., 505 U.S. 504, 112 S. Ct. 2608, 120 L. Ed. 2d 407 (1992).

[22] Geier v. American Honda Motor Co., 529 U.S. 861, 120 S. Ct. 1913, 146 L. Ed. 2d 914 (2000).

[23] Napier v. Atlantic Coast Line R. Co., 272 U.S. 605, 47 S. Ct. 207, 71 L. Ed. 432 (1926).

[24] Kurns v. R.R. Friction Prods. Corp., 132 S. Ct. 1261 (2012).

[25] Riegelv. Medtronic, Inc., 552 U.S. 312, 128 S. Ct. 999, 169 L. Ed. 2d 892 (2008).