A product generally has a design defect if, because of its design, (1) it failed to perform as safely as an ordinary user would expect when the product was used in a manner reasonably foreseeable to the manufacturer; and (2) at the time the product was designed, a safer alternative design was available that was technically and economically feasible under the circumstances.

If a product has a design defect, the manufacturer will generally be strictly liable in tort for damages caused by the defective product. This means the manufacturer will be liable even if the manufacturer exercised great care in designing the product and was not negligent.

But even when a product is defective due to a flawed design, some courts will use one of these two tests to determine whether the defendant is liable to the plaintiff:

• Risk-Utility or Risk-Benefit Test. The risk-utility test provides that a defendant is not liable for a design defect if the evidence shows the product’s utility outweighs its inherent risk of harm.

• Consumer Expectation Test. Under the consumer expectation test, the question is whether a reasonable consumer would find the product defective when using the product in a reasonable manner. If a reasonable consumer would not find the product defective when using it in a reasonable manner, the defendant is not liable even if the product’s design flaw caused the plaintiff’s injury.

Products liability laws vary from state to state and may be in a state’s statutes or in its court opinions (also known as case law or common law).

In Washington State, product liability for design defects is governed by both statutory law and case law. Under RCW 7.72.030, a product is considered to have a design defect when it is not reasonably safe as designed, meaning it fails to perform as safely as an ordinary consumer would expect when used as intended or in a manner reasonably foreseeable by the manufacturer, or when the benefits of the design do not outweigh the risk of harm posed by the product. Additionally, at the time the product was designed, there must have been a practical and economically feasible alternative design that would have reduced or prevented the harm. Washington courts may apply the risk-utility test or the consumer expectation test to determine liability. The risk-utility test weighs the product's risks against its benefits, while the consumer expectation test considers whether the product meets the safety expectations of a reasonable consumer when used as intended. If a product is found to have a design defect, the manufacturer may be held strictly liable for damages, meaning liability does not depend on the manufacturer's negligence or care in designing the product.