英汉法律词典上的解释是这样的：间接来源规则，附加来源规则。指如果受伤害人接受为其伤害补偿的来源是与侵权人无关，则损害赔偿的补偿不得因此而减少，且侵权人必须支付的规则。

What is the collateral source rule？

The collateral source rule is a common law evidentiary rule that prohibits a defendant from introducing any evidence that a plaintiff has been or will be reimbursed by any other person or organization for damages claimed in a lawsuit. For example， many plaintiffs receive compensation for medical bills or lost wages via health insurance， disability insurance or workers' compensation， but the hospital， physician or other health care provider being sued is not allowed to tell the jury about this other source of compensation. Even after these "collateral source payments" have already been paid to the person bringing the lawsuit， that person is allowed to try to collect it a second time in their lawsuit. As a result， plaintiffs often are paid twice for the same damages——that is why this is sometimes referred to as double recovery.

Why do we need collateral source rule reform？

First， it just does not make sense to allow the plaintiff to collect twice for the same medical bills or other economic losses. This drives up the cost of health care for all of us.

Worse yet， it encourages extra and unnecessary usage of health care items and services， if not outright fraud and abuse， here's why. When plaintiffs can recover twice for the same medical bill——once from their insurance and once from the defendant in the lawsuit——they （and especially their lawyer） can start to see this as a money making venture. The more medical bills they run up， the bigger their windfall. For example， if they incur $100，000 in medical bills and that is paid by their insurance， but they then get to collect the $100，000 in their lawsuit， they see that they have made $100，000 on this transaction and have incentive to try to increase the amount. The lawyer working on contingency fee benefits too since he or she gets anywhere from 30-50% of the damage money paid to the plaintiff， so if plaintiff gets an extra $100，000， the lawyer gets an extra $30，000 to 50，000.

Many states， recognizing the problems the collateral source rule was causing， have passed some form of collateral source rule reform. Nineteen states mandate that the judge offset from plaintiffs' damage awards the payments received from collateral sources. Another eleven leave it up to the jury （or judge as fact finder）， and simply allow defendants to introduce evidence of collateral source payments and have the jury or judge decide how much to offset