What happens to a damages award for patent infringement when the patent is later revoked or amended?

The Supreme Court has held that where a patent is valid and infringed, and that patent is subsequently revoked or amended (whether in England or at the European Patent Office), the defendant is entitled to rely on the revocation or amendment on the inquiry to damages.

In Virgin Atlantic Airways Ltd v Zodiac Seats UK Ltd, Zodiac had been subject to a Court of Appeal decision that held that it had infringed one of Virgin’s European patents and an order was made, among other things, for an inquiry as to damages. Subsequent to the Court of Appeal decision, the Technical Board of Appeal (TBA) of the European Patent Office ruled that the relevant claims of Virgin’s patent were invalid as they were anticipated in the prior art. It retrospectively amended the patent so as to remove, with effect from the date of grant, all the relevant claims.

The issue before the Supreme Court was whether Virgin was, as it maintained, nonetheless entitled to an inquiry as to damages. Essentially, Virgin relied on the doctrine of res judicata. This is the doctrine that prevents a party from re-litigating any claim or defence already litigated or that could have been litigated previously. The doctrine is intended to ensure the finality of judgments and to protect litigants from multiple litigation involving the same claims or issues. Virgin contended that for Zodiac to rely on the TBA’s amendment to the patent would be inconsistent with the orders made by the Court of Appeal. Zodiac’s submission was that the issue of res judicata did not arise because the issue was not one that had been addressed by the Court of Appeal as the relevant claims, considered before by the Court of Appeal, were now deemed in fact never to have existed. The amended patent, in the form that now existed, had never been considered by the Court of Appeal…

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