When someone fails to perform a duty which he or she is legally obligated to do, this is known as nonfeasance. In a simple example of nonfeasance, someone might be hired to perform a job and then simply fail to show up. In this case, the individual is legally liable because he or she has not done something as expected.
This concept is closely related to malfeasance and misfeasance. Malfeasance involves a deliberate act of wrongdoing, while misfeasance involves an action which is legally undertaken, but done badly. For example, if a teacher gives a child a peanut when the child has a known peanut allergy, this is malfeasance. If the same teacher fails to act appropriately during an allergic response, this could be termed misfeasance, while if the teacher failed to stop the child from eating a peanut butter sandwich held by a friend, this would be nonfeasance.
People may be legally obligated to perform actions for a variety of reasons. Usually, nonfeasance is related to an official duty which is spelled out in a contract, although people can also be held liable for nonfeasance if the court deems that it was reasonable to expect them to engage in an action. For example, if someone loans out their car and later remembers that the brakes are faulty, he or she could be sued for nonfeasance if the person who borrows the car becomes injured.
There are situations in which people may feel a moral obligation to do something, but they have no legal obligation to do so. Witnesses to a drowning, for instance, may feel that they should jump into the water to assist the victim because the idea of standing by and watching seems morally repugnant. However, if those witnesses failed to act, they would not get in trouble for nonfeasance, because they have no legal obligation to assist the victim. In fact, in some regions, if a witness helps the victim and the victim becomes injured, he or she can bring suit against the good Samaritan.
Nonfeasance and negligence are very similar concepts, but they work slightly differently. In the case of negligence, the damage is caused by someone's lack of proper caution. In the case of negligence, it must be proved that the person did not behave like a reasonable person would in the same situation, thereby causing damages. When someone is brought to court for nonfeasance, the party bringing the suit must simply prove that the individual failed to act.