Unlike design defects, manufacturing defects usually exist in one or a few items, rather than every product in a line. They are aspects of the product that the manufacturer did not design or intend. Instead, they occur when a product deviates from its intended design, regardless of how much care the manufacturer took to design the product, select materials, and oversee its production.
A manufacturing defect occurs during the construction phase of products. For example, an airbag that lacks the proper mechanism to deploy probably has a manufacturing defect. Similarly, a bottle of cough syrup that is contaminated probably has a manufacturing defect. Any manufacturing defect that causes an injury can give rise to a product liability lawsuit.
Generally, manufacturing and quality assurance controls limit the number of defective products that are shipped to consumers. However, occasionally a badly manufactured product bypasses the systems that are in place to make sure that it is not defective. The two most common defects involve low-quality materials and poor workmanship while assembling components to make the finished product. Often, the manufacturing defect could be eliminated if a more careful worker or better-quality materials were used to create the product. If an injury-producing problem would still be there, whether or not the product was put together well, the issue is probably a design defect rather than a manufacturing defect.
When a badly manufactured product leaves the manufacturer and causes injury when used for its intended purpose, the manufacturer is liable for any injuries that result under the principle of strict liability. Liability arises even if the manufacturer was very reasonable and careful when putting together the product. A plaintiff trying to prove strict liability need only show that the product was defective and that the defect caused his or her injuries.
Proving Manufacturing Defects
Although suing under a theory of strict liability is more straightforward in some ways than suing for negligence, it can be challenging to prove that a manufacturing defect was the actual and proximate cause of the accident. Sometimes, a plaintiff's own actions contribute to an accident, and the defendant argues that the plaintiff's actions, not the defect, caused his or her injuries.
Suppose, for example, there is a head-on collision before which the plaintiff was swerving in and out of traffic and moves into the oncoming traffic lane in order to pass the car in front of her. Even if there is a manufacturing defect in the steering such that the plaintiff cannot get out of the way of an oncoming car, the defendant will have a strong argument that the plaintiff's comparative negligence in driving into the oncoming lane contributed to the accident.
After an accident, it is important for an injured person to retain the product that caused the injury so that an expert can examine it and determine whether it has manufacturing defects. What happens if the product is so badly damaged that an expert cannot evaluate whether it malfunctioned? In some jurisdictions, a plaintiff may use the "malfunction doctrine" to show causation when the product is too damaged after the accident to determine if it had flaws. This doctrine allows a plaintiff to show that the circumstances of an accident indicate that a defect caused the accident and to present evidence eliminating all other possible causes to show that a flaw must have existed at the time of the sale.
A defendant manufacturer can defend a manufacturing defect lawsuit in two primary ways: arguing modification or arguing assumption of the risk. With modification, the defendant must prove that the product was changed since it left the defendant's possession. To prove assumption of the risk, the defendant will need to demonstrate the plaintiff knew of the hazard that hurt him or her and chose to engage in the activity nonetheless.