Legal Definitions - malfunction theory

The malfunction theory is a principle in products liability law that allows a person to prove a product was defective by demonstrating that the product simply failed to work as intended, rather than requiring them to identify and prove a specific flaw in its design or manufacturing.

Ordinarily, to win a products liability case, a plaintiff must show a specific defect, such as a faulty component, an error in the manufacturing process, or a dangerous design. However, sometimes a product malfunctions in a way that strongly suggests a defect, but the exact cause is difficult or impossible to pinpoint after the fact. The malfunction theory provides a pathway for justice in such situations.

To successfully use the malfunction theory, the plaintiff typically must also show that:

• The product was being used correctly and was not misused.
• All other reasonable explanations for the malfunction, apart from a defect in the product itself, have been ruled out.

Here are some examples illustrating the malfunction theory:

• Example 1: Unexpected Appliance Failure

  A consumer purchases a brand new, high-end coffee maker. On its second use, while brewing a standard pot of coffee according to the manufacturer's instructions, the machine suddenly sparks, emits smoke, and completely stops working. An inspection by an expert technician cannot identify a specific faulty wire, circuit board, or component that caused the failure, but confirms the machine is inoperable due to an internal electrical malfunction. The consumer did not drop the coffee maker, use it with an incorrect power supply, or tamper with it in any way.

  This illustrates the malfunction theory because: The coffee maker clearly malfunctioned under normal, intended use. While a specific defect (e.g., a particular faulty resistor) cannot be identified, the sudden and complete failure, combined with the absence of misuse and the ruling out of external causes, strongly suggests an inherent defect in the product.

• Example 2: Safety Device Failure

  A family installs a new smoke detector in their home. Months later, a small electrical fire breaks out in an adjacent room. Despite the fire producing significant smoke, the smoke detector fails to activate and emit an alarm. After the fire is extinguished, investigators examine the smoke detector and find it appears physically intact, with fresh batteries, and no obvious signs of damage or tampering. They cannot pinpoint a specific manufacturing error in the sensor or alarm mechanism, but it simply did not perform its essential safety function.

  This illustrates the malfunction theory because: The smoke detector, a critical safety device, failed to operate as designed during an actual emergency. Even though the specific internal defect causing the failure cannot be precisely identified, the fact that it malfunctioned under conditions it was designed to detect, without any evidence of misuse or external interference, supports the claim that it was defective.

• Example 3: Vehicle Component Failure

  A driver is operating their car on a highway when, without warning or any prior indication of trouble, the steering wheel suddenly locks up, making it impossible to control the vehicle. The driver was not speeding, driving recklessly, or performing any maneuvers that would stress the steering system. After the resulting accident, mechanics inspect the vehicle but cannot find a broken steering rod, a disconnected hose, or any other specific, identifiable mechanical failure that caused the lock-up. The steering system simply ceased to function properly under normal driving conditions.

  This illustrates the malfunction theory because: The car's steering system, a fundamental safety component, malfunctioned completely and unexpectedly during normal operation. Despite the inability to identify a precise broken part or manufacturing flaw, the sudden and catastrophic failure, coupled with the absence of driver misuse or other external factors, points to an inherent defect in the product.