How Is Fault Proven in a Product Liability Case?

Defective products injure thousands of consumers every year. Fortunately, consumers are protected under product liability law and may recover damages from manufacturers who sell defective products. Manufacturers must make sure that their products meet the ordinary expectations of users. For example, birth control users wouldn’t expect to suffer a heart attack as a result of taking the pill.

A product is defective if it carries a design defect, manufacturing defect, or a defect in warning.  If the product contains one or more of those defects, the next step is proving how the manufacturer is at fault for the defective product in order to recover damages. There are several theories of liability that the plaintiff can use to prove fault. The most common theories are strict liability, negligence, and breach of warranty.

Strict Liability

Strict liability means that the manufacturer is liable for your injury, regardless of any precautions that were taken to prevent the harm. In other words, you won’t need to show that the manufacturer was careless in producing the product. However, you will need to prove that the product was unreasonably dangerous and that defect caused your injuries.

For example, drospirenone birth control pills have been reported to cause blood clots at a higher rate than other types of birth control pills. If drospirenone is shown to be an unreasonably dangerous ingredient in birth control pills, manufacturers could be held strictly liable for the blood clots caused by the pill, since no amount of care would make the pills safe to use.


Negligence looks at how reasonably careful the manufacturer was in producing the product. To prove negligence, you must show that:

  • The manufacturer had a duty to make the product safe,
  • It breached that duty by not taking reasonable steps to ensure the product was safe, and
  • You were injured as a result of this breach.

For example, a drug manufacturer that knows its product contains an ingredient that can cause heart attacks, but doesn’t warn consumers about the risk could be found negligent if a user suffers a heart attack because of taking the drug.

Breach of Warranty

A warranty is the manufacturer’s guarantee about the quality of a product. When a product fails to live up to this guarantee, the consumer can often sue the manufacturer for breach of warranty. There are two types of warranties: express and implied warranties. An express warranty is usually found on the label, packaging, instructions sheet, or advertisements. For example, if a ladder that’s advertised to hold up to 300 pounds collapses when someone who weighs 150 pounds uses it, the manufacturer may be liable for breach of an express warranty.

An implied warranty is one that isn’t expressly stated by the manufacturer but applies to the product automatically. There are two types of implied warranties: the implied warranty of merchantability and the implied warranty of fitness for a particular purpose. An implied warranty of merchantability is a promise that the product is reasonably suitable for its intended use. For example, a baby teething ring that contains toxic material breaches the implied warranty of merchantability, because anything containing toxins is not suitable to use as a teething ring.

Similarly, an implied warranty of fitness is a guarantee that the product is reasonably fit for the advertised purpose. For example, if you buy an acne cream to clear up your skin and it causes you to breakout even more, the manufacturer may be liable for breach of the implied warranty of fitness.