Defective Product Claims: Theories of Liability

Different claims ("causes of action") can come into play when you're suing over injury or illness caused by a dangerous or defective product.

If you've suffered injury or illness because of a defective or dangerous product, medication, medical device, or other manufactured item, you might have a viable product liability claim. These kinds of cases can arise when a single product (or a small batch of the same product) is faulty, or when an entire product line is blamed for causing certain kinds of illness. Claims that arise in this latter situation are sometimes called "mass tort" cases, and recent examples include lawsuits over the safety of Roundup and Zantac/ranitidine.

In this article, we'll explore the most common fault theories in product liability cases, including:

  • strict liability
  • breach of warranty
  • deceptive marketing, and
  • negligence.

Strict Liability

If there is an "ace in the hole" in product liability claims, it is the legal doctrine of strict liability. Here's how strict products liability works:

Normally, if a company is the cause of harm of some sort, the company will only be held liable if it is found to have acted negligently—in other words, the company did not take normal care or precautions. If you slip and fall in a store, for example, the business will only be liable if you can show that it (or one of its employees) was negligent. With strict liability, however, the company will be liable regardless of whatever care it exercised or precautions it took to prevent an injury or illness.

As a practical matter, strict liability means that when you present your product liability claim, you don't need to show that the manufacturer or supplier of the defective product was not sufficiently careful in making or distributing that product. You just have to show that the product is somehow defective and that the defect was the cause of your injury.

In opposing your defective product claim, the defendants in your case may argue that the product was not unreasonably dangerous, that you should have been aware of the danger and avoided it, or that the defect was not the cause of your injury. But if you are able to base your claim on strict products liability, the defendants will not be able argue that they were really, really careful when they made or distributed the defective product.

Deceptive Marketing/Fraud

In some cases, the evidence may show that a defendant knew of a danger associated with a product and deliberately concealed the danger or marketed the product using deliberately misleading statements. In such cases, you may have a claim for deceptive marketing or intentional misrepresentation, or a tort claim based on the fraudulent conduct (the names may vary from state to state).

If the defendant is a corporation, what the defendant "knew" may be based not on information hidden in someone's brain (or memory), but rather on information contained in a company's records.

For example, a 2018 Reuters investigative report suggests that Johnson & Johnson knew about the presence of asbestos in products like Johnson's Baby Powder for decades, based on extensive review of company documents. Learn more about lawsuits linking talc products to cancer.

Breach of Warranty

Many products come with some sort of warranty or guarantee. You might have a defective product claim if the defect in your product violated (or "breached" in legalese) that warranty.

An "express warranty" is any type of warranty or guarantee that is written or stated. Such written statements can be:

  • on the product's label or packaging
  • in the instructions or other paperwork included with the product
  • on signs or other marketing materials at the store where you purchased the product, or
  • in any form of advertising for that product.

Any of these representations about the defective product may be an express warranty.

If the product you used did not come with an express warranty, that product may be covered by implied warranties, and the defect may have violated those implied warranties.

An "implied warranty" is a warranty that the law automatically applies to your product—it doesn't have to be guaranteed by the manufacturer. State law imposes these warranties on manufacturers and suppliers, whether they like it or not.

The implied warranties that apply to your case will depend on the particular product involved and the circumstances surrounding its sale. Though they may differ somewhat from state to state, implied warranties generally come in two forms:

Implied warranty of merchantability. This is a guarantee that a product is reasonably fit for the purpose for which it was sold. For example, if you purchase sunglasses that have no UV protection and suffer eye damage as a result, you would likely have a claim for breach of the implied warranty of merchantability because any sunglasses on the market can be expected to provide UV protection.

Implied warranty of fitness for a particular purpose. This imposes an additional obligation in cases where a seller knows that the buyer of a product intends to use it for a particular purpose. This warranty is an additional guarantee that that product will be reasonably fit for that purpose. For example, if you go to the hardware store and ask for a weed trimmer capable of cutting through bamboo of a certain thickness and you are subsequently injured because the trimmer you were sold breaks while using it in the very way you specified, you would likely have a claim for breach of the implied warranty of fitness for a particular purpose.


In addition to a claim based on strict products liability, or in cases or jurisdictions in which strict liability is not an available legal basis for your claim, you may be able to argue that defendants acted negligently in manufacturing or supplying the defective product that left you injured or sick.

In order to prove negligence, you must show that the defendants were not reasonably careful (called "failing to exercise reasonable care") in making or distributing the injury-causing product. Proving negligence can be difficult—but the difficulty varies depending on the type of product and manufacturing involved. For example, showing that a huge pharmaceutical manufacturer's quality-control engineers failed to exercise reasonable care may be impractical; on the other hand, it may not be so difficult to prove that a scooter dealer failed to institute a reasonable system for inspecting the brake pads on the scooters it has for sale.

Next Steps

Keep in mind that if you think you have a viable product liability case, you can use one or more of the above-discussed theories in the same lawsuit. For example, a Roundup lawsuit might include allegations that Bayer should be held strictly liable for selling an unreasonably dangerous product, and that the company engaged in deceptive marketing by hiding known links between the popular weed killer and illnesses like non-Hodgkin's lymphoma.

If you're thinking about suing a manufacturer for injury or illness tied to a product or medication, an experienced lawyer will help you devise the right strategy and realize the best outcome. Get tips on finding the right personal injury lawyer for you and your case.

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