In Estudillo v. Security Loan etc. Co. (1906) 149 Cal. 556, the plaintiffs had suffered a default judgment in a prior action in which their motion to set aside the judgment was denied.
They subsequently filed a suit to vacate the judgment, alleging the same "facts" of which they were aware when they brought the motion. The second action was dismissed on demurrer.
The Supreme Court reversed, concluding that res judicata and collateral estoppel did not apply. As the court explained:
"The burden of proof rests upon no one more heavily than upon a plaintiff seeking relief upon the ground of fraud, and he ought not to be unduly hampered as to the means of making proof. In support of a motion he is limited to ex parte affidavits of voluntary witnesses unless the court in its discretion permits a wider latitude. In a separate suit he may bring unwilling witnesses into court by subpoena, and he may take their depositions. The remedy is ampler and more efficacious, and the case is one which demands the amplest and most efficacious remedy. . . .
". . . 'In a subsequent action to set aside a judgment on the ground of fraud, neither the judgment thus sought to be vacated, nor an order in the prior case refusing to set aside a default . . . can be set up as a bar to the subsequent action.' From which it would seem to follow that in such a case as this the correct practice would be to move promptly under section 473 of the Code of Civil Procedure in the prior action, and if defeated in that proceeding to commence a separate action for relief upon the ground of the former plaintiff's fraud - a practice to be commended as convenient and expeditious in case the motion should be granted, and as affording the injured party all the advantage of a regular trial of the issue of fraud if the more summary proceeding proves ineffectual." (Estudillo, supra, 149 Cal. at pp. 564-565.)
Section 473, subdivision (b) of the Code of Civil Procedure permits a judgment to be set aside on the grounds of mistake, inadvertence, surprise, or excusable neglect.