Articles on Law, Science, and Engineering

REAL USERS VERSUS IDEAL USERS[index]

The legal doctrine of products liability evolved from a series of court decisions in cases involving real users of products. Most products liability cases involve mass market devices such as power saws and lawnmowers. The rules that emerge from these cases are based on the assumption that the user of the product is a reasonable person. The definition of a reasonable user is extremely contentious. As an illustration, "reasonable" lawnmower users have: used lawnmowers as hedge trimmers; given children rides while cutting the grass; and used their hands to remove debris from the turning blade. Lawnmower manufacturers have been found liable for not engineering protection to prevent these "reasonable misuses."

It is important to understand how the law reaches the conclusion that a manufacturer should foresee that people will stick their hands in running lawnmowers. Smart people do stupid things with machines. Physicians, attorneys and even engineers stick their hands in lawnmowers. When otherwise reasonable people have stupid accidents, jurors assume that the accident should have been prevented by the manufacturer. Since lawnmowers may be operated by inexperienced users, the law requires that lawnmowers be designed to protect these users.

The law does not require that airplanes be idiot proof because airplanes are only used by trained pilots. If airplanes could be flown by untrained users, they would have to be designed to protect untrained users. Since it would be impossible to design an idiot proof airplane, the airplane industry exists only because various legal restrictions prevent untrained or incompetent pilots from flying airplanes.

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