The United States collateral source rule, otherwise known as collateral source doctrine, is a part of common law that denies arguments that a victim's damages were or will be compensated from elsewhere. In a civil case, such as an accident where personal injury took place, a defendant may attempt to argue this hoping to relive their duty of damages. A common example of this type of attempted defense is when a defendant claims their damages will be paid by the victim's insurance — this type of evidence would be prohibited in court, as a result of the collateral source rule. It is important to know, also, that the collateral source rule has changed due to controversy frequently in some states recently.