Defective Product Claims: Theories of Liability

Learn the common liability theories used in defective products cases.

If you have been injured or suffered other damages because of a product you used, you may have a defective products claim against the manufacturer, retailer, or other party in the chain of distribution.

There are four theories of liability commonly used in defective products cases. Understanding these theories will help you decide if you want to pursue a defective products claim. Keep in mind that you can use one or more of these theories at the same time. Here's a brief overview of the theories. (To learn how to identify defendants in your defective products claim, read Nolo's article Defective Products Claims: Who to Sue?)

Breach of Express Warranty

Many products come with some sort of a written 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.

For example, say you want to buy a weed trimmer to trim the bamboo shrubs in your backyard. You see an advertisement in a gardening magazine for Brad's Burly Bamboo Trimmer, which is shown trimming bamboo much thicker than yours. At the hardware store, you find the same product in a section with a sign: "Heavy-Duty Trimmers." The instructions that come with the trimmer state: "Safe for use with bamboo up to half-inch thickness."

When you first use your new trimmer, the blade catches on a one-quarter-inch-thick bamboo shoot, flies off the motor, and slices several of your fingers off. The magazine advertisement, the store sign, and the instructions might each be considered an express warranty, and you would include claims for breach of all of these express warranties in your defective product lawsuit (as well as additional claims discussed below).

Breach of Implied Warranty

If the defective product you used did not come with an express warranty -- and even if it did -- 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 or store where you bought the defective product. State law imposes these warranties on product 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.

Strict Products Liability

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

Normally, if a company is the cause of an accident 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 in its actions (called the failure to "exercise reasonable care"). With strict liability, however, the company will be liable regardless of whatever care it exercised or precautions it took to prevent an accident.

As a practical matter, strict liability means that when you present your defective product 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.

Strict products liability is a rapidly developing area of the law and its application varies considerably from state to state. Most states have adopted some version of strict products liability, but it may not be available in every case.


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 injured you.

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 moped dealer failed to institute a reasonable system for inspecting the brake pads on the mopeds it has for sale.

Intentional Misrepresentation or Fraud

In some cases, the evidence may show that a defendant knew of a dangerous defect 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 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, if you were injured by a drug you took, and you or your lawyer discover company records indicating that the manufacturer was aware of the danger but chose deliberately to conceal it (perhaps to shield the company's profits), you may have a claim for intentional misrepresentation.

Getting Help

Products liability cases can be complicated, and some claims may involve large amounts of money for injuries or damages. Depending on your case, you may wish to retain the services of a lawyer who specializes in products liability. For help on choosing a good personal injury attorney, read Nolo's article Finding a Personal Injury Lawyer. Or, you can go straight to Nolo's Lawyer Directory for a list of personal injury attorneys in your geographical area.

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