Step 1 of 3


  • The information you submit will be shared with advertising attorneys. By clicking submit, you agree to being contacted by an attorney. Privacy Policy

How is Fault Proven in a Product Liability Case?

People injured by defective products can sue those responsible to receive compensation. To win a lawsuit, a plaintiff usually must prove that someone is at fault – to blame – for an injury. Fault in product liability law can differ depending on the relevant law. This article focuses on proving fault under the three main theories for product liability: strict liability, negligence, and breach of warranty.

Strict Liability

Proving fault in product liability cases is relatively easy using strict liability. That’s because strict liability doesn’t require proof of fault. Instead, it only requires proof of injury from the manufacturer’s defective product. In other words, if a person is injured by the defendant’s defective product, the defendant is liable under strict liability.

Consider how this might work in a transvaginal mesh case. In a standard product liability case, manufacturer Ethicon might be liable if its transvaginal mesh products injured a patient. If a lawsuit is brought using strict liability law, the injured plaintiff would only need to prove that she received transvaginal mesh from Ethicon, and that she was injured by a defect in the product. No proof that Ethicon acted wrongly would be required.


A person can also win a product liability lawsuit by proving that his or her injury resulted from the manufacturer’s negligence. The law has developed a specific but complicated formula for proving negligence. To recover damages, a person must prove that:

(1)   The manufacturer owed a duty of care to the plaintiff.

(2)   The manufacturer breached that duty of care.

(3)   The breach of duty actually caused the plaintiff’s injury.

(4)   The breach of duty was the proximate cause of the plaintiff’s injury.

(5)   The plaintiff was damaged by the manufacturer’s conduct.

Unlike strict liability and breach of warranty (see below), the manufacturer’s fault is central to a negligence case. In other words, a plaintiff must prove that the manufacturer was negligent in making the product that injured her. The law measures a manufacturer’s negligence by asking whether its conduct was reasonable among manufacturers of similar products.

Consider how the hypothetical lawsuit against Ethicon might work here. A plaintiff would still need to prove that she was injured by Ethicon’s transvaginal mesh. But if the lawsuit alleges negligence, she would also need to prove that Ethicon was negligent in making the transvaginal mesh – injury alone would not be enough. This would likely require expert witnesses testifying about Ethicon’s production process compared to the rest of the industry.

Breach of Warranty

Many sellers guarantee the quality of a product to make a sale. These are called warranties. “Satisfaction guaranteed or your money back” is an example of an express, or stated, warranty. There are also implied, or unstated, warranties imposed by law guaranteeing that a product will work as it’s supposed to work.

Proving fault is not central to breach of warranty cases. This is because warranty law comes from contract law, and is therefore focused on contracts. When a seller promises “satisfaction guaranteed or your money back,” contract law allows a consumer to get his or her money back if unsatisfied with the product. The seller’s fault usually doesn’t matter.