When a party is harmed, that typically gives rise to a claim for damages. However, an express limitation to the extent of recovery for those damages is those that could be avoided by the injured party engaging in reasonable and ordinary care after the harm. The failure of the injured party to engage in reasonable and ordinary care after the harm serves as an affirmative defense by any defendant to the claim for damages.
Stated another way, under the “common law doctrine of avoidable consequences,” one injured by another’s tort is not entitled to recover damages for harm he or she could have avoided by the use of reasonable effort or expenditure after the tort was committed. The defendant who raises failure to mitigate as a defense must offer evidence showing the extent to which damages would have been reduced (or the injury have been less serious) if steps to mitigate had been taken.
Please keep in mind that the avoidable consequences doctrine (sometimes inaccurately characterized as a “duty” to mitigate damages) does not require an injured person to do the unreasonable or impracticable; the plaintiff is not required to make expenditures that he or she is financially unable to make.
This defense often arises in the context of a tort case (i.e. personal injury, etc.). However, it is also common in wrongful termination and breach of contract cases. Employees wrongfully terminated and put out of work for months or years may have their recovery limited in the event efforts were not made to minimize the damages experienced as a result of the termination. Similarly, contract damages could be limited in some cases where it would have been reasonable for the victim to enter an agreement for work in place of the lost contract.