If, for example, an individual is sick and unable to make a critical decision, agency of necessity would allow an attorney, parent or spouse to make decisions on behalf of the incapacitated party.
Agency by necessity refers to a situation where an agent by necessity makes a critical decision on behalf of another party who is not in a condition to do so. For example, if Person A was severely injured in a car accident and was in a coma, Person B could make the decision to allow medical staff to operate on Person A. Under normal circumstances, Person A would have to give consent, but if he or she was unable to do so, an agent can make the decision instead.