Product liability is that section of the law that requires the manufacturer to make reasonably certain their product is safe. Each year thousands of people are injured due to unsafe products. Examples run the gamut from high tech prescription medication with undisclosed or unacceptable side effects to simple every day items such as step stools without a sufficiently wide base and are too easy to tip over.

In essence all product liability cases stem from three basic principals;

The product is defective. A problem with the manufacture of the product resulted in an injury. Examples; improper welds resulting in product failure during use, foods or drugs contaminated during the manufacturing process. The general safety of the product is not called into question, only the condition of the one example of it that resulted in injury. 

The design is defective. In these cases the argument is that there is something inherent in the design that results in the product being unsafe under certain conditions. Recent headlines include vehicle and drug recalls. Often these product fail to meet certain industry standards for safety. These standards are constantly changing. For example small appliances made without ground fault interrupters may have been standard 10 years ago, but if this safety device were not included in such a product made today, it would be considered an inherently unsafe design.

The manufacturer failed to warn of potential hazards. In many cases it is impossible to make a product completely safe. The law understands this and allows for the manufacture of products with potential safety issues provided the user is warned the the issue. For example ladders are inherently unsafe. They may be used with a reasonable level of safety provided the user is warned of three issues (1. Be careful, there is always risk of a fall. 2. Place the ladder on a firm level surface. 3. Do not stand on the top x steps.) If a ladder company fails to include these basic warnings and a user is injured as a result then the ladder company is at fault.