Collateral source rule

The collateral source rule, or collateral source doctrine, is an American case law evidentiary rule that prohibits the admission of evidence that the plaintiff or victim has received compensation from some source other than the damages sought against the defendant. For example, in a personal injury action, evidence that the plaintiff's medical bills were paid by medical insurance, or by workers' compensation, is not generally admissible.
The collateral source doctrine has come under attack by tort reform advocates. They argue that if the plaintiff's injuries and damages have already been compensated, it is unfair and duplicative to allow an award of damages against the tortfeasor. As a result numerous states have altered or partially abrogated the rule by statute.