The importance of careful selection of prior art

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Mr Justice Birss has refused [1] an application by the defendant in patent proceedings to re-open the trial and to permit it to amend its pleadings to plead new prior art. Birss J had himself given judgment in the case in November in which he found that the claimant’s telecommunications patent to be valid and infringed by the defendant. The prior art that the defendant now wished to adduce comprised three documents found by employees of the defendant two weeks after Birss J handed down his judgment.

Birss J accepted that he had power to re-open the trial but declined to do so. In doing so he considered the following well-established principles:

  • Could the evidence have been found with reasonable diligence before the trial?
  • Would the evidence, if given, probably have an important influence on the results of the case?
  • Was the evidence on the face of it entirely credible?

The application had to be considered in the interests of efficient litigation, justice to others and use of court resources. The prior art had been available before the trial and could have been found with reasonable diligence. Although neither party had acted to their detriment in reliance on the judgment and there would be no major prejudice to the claimant if the matter were to be re-opened, that did not justify re-opening the trial, where there was no excuse for the defendant not having adduced the prior art at trial. Further, it was not clear that even with the prior art, the patent in suit would be invalid.

The lesson to take home from this case is to ensure the right prior art is selected and adduced before trial. Afterwards it will be too late. In the judge’s own words, the application “could and should have been made before trial and then it would not have had the serious consequences for the resources and finality which it now has and it would not have the serious impact on other court users which it now would have”.


[1] Vringo Infrastructure Inc v ZTE (UK) Ltd [2015] EWHC 214 (Pat)