Liability Rules

Liability Rules

In tort cases, the courts must have a means of deciding whether or not a defendant should be held liable for damages suffered by the plaintiff.  Many different doctrines have been used, but there are two main streams of thought:

Strict liability.  Under a strict liability doctrine, a defendant will be held liable for any damages to the plaintiff, so long as conditions of causation are met.  For instance, a strict liability approach to product liability would say that if you were injured by your lawnmower, the lawnmower manufacturer would have to pay damages regardless of how much care was taken in the production of the lawnmower. 
Negligence.  Under a negligence doctrine, a defendant will be held liable for damages only if he took less care than he should have taken.  The amount of care a defendant should have taken is called "due care," which is defined as the amount of care a reasonable person would have taken under the same circumstances.  To take the lawnmower example, a negligence approach might say that if the lawnmower manufacturer had inspectors on the factory floor, did product safety testing, and attached clear safety guidelines for consumers, then it would not have to pay damages for injuries from its lawnmowers. 
These doctrines rarely exist in their pure form.  Actual legal rules often incorporate elements of both approaches.  For instance, strict liability is usually modified with a rule of contributory negligence, which exempts the defendant from liability when the plaintiff failed to take due care.  (In the lawnmower example, the manufacturer might avoid liability because the injured consumer did not follow the safety guidelines.)  In negligence, some activities (such as failing to abide by a public safety ordinance), are deemed "negligence per se," which means doing them at all creates liability for any harm that might occur.  For example, a landlord who failed to maintain his fire escapes would automatically be held liable for damage caused by them.