Closely akin to the doctrine of res adjudicata is that which will not allow a court of equity to grant relief against a fraudulently acquired judgment unless the fraud is shown to have been "extrinsic" or collateral rather than "intrinsic" fraud. According to this rule, to warrant equitable relief against a judgment on the ground of fraud, it must appear that the fraud was practiced in the very act of obtaining the judgment. Relief is granted on the theory that through fraud extrinsic and collateral to the actual proceedings before the court, the unsuccessful party has been prevented from fully presenting his case, and hence that there has never been a real contest before the court on the subject matter of the suit. On the other hand, the rule is that an issue or controversy which has once been tried and passed on by a court should not be retried in an action for relief against the judgment, since otherwise litigation would be interminable.
Harold C. Dedman,
Intrinsic and Extrinsic Fraud and Relief against Judgments,
4 Vanderbilt Law Review
Available at: https://scholarship.law.vanderbilt.edu/vlr/vol4/iss2/6