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If the defect is a manufacturing defect, it may be easier to establish the problem, since the product does not meet the manufacturer's own design or specifications. Comparison of the defectively made product to others made according to the same specifications will often satisfy the legal proof requirements. If you believe that a product with a manufacturing defect may have caused you injury, you should be aware that it may be essential to keep whatever is left of the defective product, even if it is in pieces, to prove the manufacturing defect.

Consumer products may also be defective due to a defect in the basic design, or where the design does not include necessary safety devices to reduce risk of injury from a danger inherent in the product. In these “design defect” cases, the product may have performed exactly as it was designed to, yet caused injury. Legal proof centers on the existence of a feasible alternative design that would accomplish the same objective while lowering or eliminating the risk of injury.