Sanhedrin 31 - Limitations on Submitting Evidence
In general, there is no statute of limitations on the submission of evidence. Even after the verdict has been issued, whenever a litigant brings evidence to support his claim, he can nullify the verdict.
If the judges found it necessary to impose a time limit and told the litigant, after issuing a verdict against him, "All evidence that you may have to support your claim, you must produce within the next thirty days," then the rule is: if he finds evidence within thirty days, he can nullify the verdict, but if he finds it after thirty days, he cannot nullify the verdict.
Rabban Shimon ben Gamliel says, "What should this person do? Rather, he may present the evidence even after thirty days." The law follows Rabban Shimon ben Gamliel.
If a litigant saw that he was about to be found liable and then produced witnesses, he is not believed, because it is a desperate attempt to win the case.
Art: Jan Cornelisz Vermeyen - Portrait of Judge John More