Res Judicata

Res judicata is the principle that once a court has finally decided an issue between parties, that decision is conclusive between them and cannot be re-litigated. The Supreme Court's 2013 decision in Virgin Atlantic Airways v Zodiac Seats UK examined the doctrine in depth: Virgin argued that the Court of Appeal's earlier findings that its patent was valid and infringed were res judicata as between it and Zodiac on the subsequent assessment of damages, while Zodiac argued that no issue of res judicata arose because that was not the situation considered by the Court of Appeal, given the European Patent Office's later retrospective amendment of the patent.

One recognised branch of res judicata is cause of action estoppel; the Supreme Court in Virgin v Zodiac held that an earlier line of Court of Appeal cases had wrongly treated cause of action estoppel as absolute generally rather than absolute only as regards points actually determined by the earlier decision. A related branch, issue estoppel, prevents a party from reopening in later proceedings a specific issue that was necessarily decided against it in earlier proceedings — a principle the Supreme Court also considered, in the arbitration enforcement context, in Dallah v Pakistan, where it held that the argument based on issue estoppel was always doomed to fail on the facts of that case.