What is needed to prove a defective product caused injury in California depends on the type of product defect claim alleged. A defective product is generally characterized as a product with any sort of imperfection or fault in the product's manufacturing, design, or labeling.Discover how California law defines liability for design defects and what it means for you. Get informed and protect your rights today. For example, a plaintiff may bring a negligence claim against a prescription drug manufacturer even if that manufacturer cannot be sued under a strict product. Judicial Council of California. Manufacturing Defect – A flaw in the manufacturing process meant the product was defective before it left the manufacturing or distribution chain. The product liability laws in California are consumerfriendly. What Constitutes a Manufacturing Defect in California? If you find yourself the victim of a defective product, file a claim as soon as possible.