Product Liability: Manufacturing Defects vs. Design Defects

When a product injures someone, a court will ask the same sort of questions you would: How did the injury happen? Was there something wrong with the product? How badly was the person injured? Although these questions seem simple, the answers can be surprisingly complex. Courts faced with the question "was there something wrong with the product?" use two general theories to analyze the facts surrounding the injury: products liability (sometimes referred to as strict products liability) and negligence.

To some extent these theories overlap or blend but the basic difference is that products liability focuses primarily on the product itself while negligence focuses on the manufacturer, seller or distributor's conduct as well as the product. Both theories look at what was wrong or defective in the product.

The Law Governing Defective Products

Product defects are generally put into three categories: design defects, manufacturing defects and marketing defects. Marketing defects are defects in the manner in which a product is sold. This type of defect can include inadequate warnings and/or instructions. Design defects are in a manner of speaking, intended. This type of defect is inherent in the design of the product. For example, a chair that is designed with only three legs might be considered defectively designed because it tips over too easily. Manufacturing defects on the other hand are defects that were not intended. For example, a chair might be designed to be stable, but if it is manufactured with one of the legs not bolted on correctly, the chair would be said to have a manufacturing defect.

Planned or Unplanned Defects

How do you decide whether the product that injured you was defectively designed or defectively manufactured? A very simplistic way to look at it is to look at whether the defect was planned or unplanned. You will find a design defect in every individual product produced according to the product plan. A manufacturing defect on the other hand is an unplanned defect. You would generally expect to find only a small percentage of manufacturing defects in a group of products produced according to a particular plan.

As noted above, manufacturing defects, unlike design defects, are not intended parts of the product. A manufacturing defect is, in essence, a mistake in the manufacturing process. Under products liability, even if the manufacturer was extremely careful in manufacturing the product, it will still be held responsible for any manufacturing defect in the product. It does not matter, for purposes of product liability, that all possible care was taken in the preparation and marketing of the product. This is why products liability is sometimes referred to as liability without fault.

The reason courts impose liability without fault is that it is believed that doing so will encourage greater investment in product safety than would a fault-based system of liability. As might be expected, this could raise the price of products. The increase in price is an intended consequence because it is believed that, as a matter of social policy, consumers who benefit from products without suffering harm should share, through increases in the prices charged for those products, the burden of unavoidable injury costs that result from manufacturing defects. Courts also believe the increase in the price of products with a high percentage of faults will discourage people from buying those products.

In a manufacturing defect case, the plaintiff bears the burden of proving that the product in question had a fault or defect. Often the manufacturer's design or marketing standards can be used to show that the product was defective. But proving how or why the flaw or defect occurred can be a difficult if not impossible proposition for the plaintiff. By eliminating the issue of manufacturer fault from the plaintiff's case, strict liability is thought to reduce the transaction costs involved in litigating that issue. Additionally, in many cases manufacturing defects are caused by the manufacturer's negligence even though plaintiffs may have difficulty proving it. Strict liability in these cases allows deserving plaintiffs to succeed notwithstanding what would otherwise be difficult or insurmountable problems of proof.

While liability without fault might not seem entirely fair at first glance, it is important to remember that manufacturers invest in quality control at consciously chosen levels. The manufacturer's knowledge that a predictable number of flawed products will enter the market place entails an element of deliberation about the extent of injury that will result from their activity. Finally, as a matter of social policy, between the innocent victims who suffer harm because of defective products and the manufacturers, distributors and sellers of products, the product sellers are in a better position than are individual users and consumers to insure against such losses.

Design defects are based on a different theory of liability than manufacturing defects. In some respects, a manufacturing defect case presupposes that if the product had been flawlessly manufactured according to its design, the injury would not have occurred. For this reason, the proof in a manufacturing defect case will often consist in part of the manufacturer's own design or marketing standards. A design defect case on the other hand attacks those very standards as inadequate. Because those standards are the very ones that plaintiffs attack as unreasonable, some sort of independent balancing is necessary.

As you might imagine, some products are not defective merely because they are dangerous. Many risks can be eliminated only by excessively sacrificing product features that make the products useful and desirable. For example, an electric knife that is too dull to injure anyone would also be useless for its intended purpose. It is generally felt that, as to such risks, users and consumers are the best equipped to minimize risk. The theory is that it is necessary to strike a balance between increased costs to consumers associated with holding manufacturers liable for their design choices and having individual consumers bear the risk by not being compensated for injuries suffered.

In trying to achieve this balance, different courts use different tests to determine whether a product is defectively designed. To some extent the tests reflect the various states' differing social policies. Some courts say that a product is defective if it is unreasonably dangerous as designed. Others say that a product is defective if it is not safe for its intended, or reasonably foreseeable use, as designed. A good example of the difference between these two versions of design defect is found in the case of cars. Imagine a person injured in an automobile accident bringing a lawsuit, which alleges that the car he was driving was defective because it was designed in such a way that it will invariably explode if involved in an impact while going more than thirty miles per hour. Some courts might argue that the car, as designed, is not unsafe because it is the action of crashing the car, not the car itself, which causes the injury. Those courts might say that since the design of the car is not unsafe, it is not defectively designed. Other courts would say that the car was defective because it was reasonably foreseeable that a user would crash the car while going more than thirty miles per hour, thus the manufacturer should design the car with such collisions in mind.

While some courts require that a product be proved both defective in design and unreasonably dangerous because of the defect, many courts have combined the defect and danger elements. In those courts a product is defectively designed if it is unreasonably dangerous because of its design. Courts use various definitions of "unreasonably dangerous" including a product that is more dangerous than an ordinary consumer would expect, or a product whose risks are so great that a reasonable seller would not place the product on the market, or a product design whose risks outweigh its benefits.

Although products liability calls for liability without fault, a plaintiff may seek to recover based upon allegations and proof of negligent manufacture or negligent design. A claim for negligent manufacture alleges that the manufacturer did not use reasonable care in manufacturing the product. A claim for a design defect under negligence alleges that the product is defective because it was designed without reasonable care. In such a case the plaintiff seeks to show how or why the product was defective. A case involving a product defect will often make claims under both negligence and products liability and many courts use a hybrid of products liability and negligence in cases involving product defects.


The law holds manufacturers, sellers and distributors responsible for products that pose a danger to users or consumers as a result of design and/or manufacturing defects. If a product has injured you, you may be able to recover for your injuries under products liability or negligence law. An attorney with experience in handling products liability and negligence cases can analyze the facts surrounding your injury and determine whether the product that injured you was defectively designed, defectively manufactured or both.