Japanese law relating to challenging patent validity changed on January 1, 2004 with the replacement of the post-grant opposition system introduced in 1996 by a new invalidation procedure.

Under the new system, an invalidation action can be started at any time during the life of the patent or in some cases even after it has expired. Furthermore, except when challenging the inventorship of a patent, a challenger to patent validity need not have any specific interest in the matter, thereby leaving open the possibility of challenges by front men rather than the real party in interest. Under the new procedure, challenges may be made on any ground under which a patent may be held to be invalid.

Under the new procedure, once the invalidation action has been filed by a third party, the patentee will have the right to respond and offer narrowing amendments if desired. If amendments are made the third party challenging validity will probably be given the opportunity to file further evidence. The issue then will be decided by a three-person panel of the Board of Appeals and Trials. The losing party will have the right of appeal to the Tokyo High Court. The losing patent owner will have the right to limit the claims during such an appeal as long as the amendment is made within ninety days of the Appeal Board decision against which it is appealing.

It remains to be seen how much use will be made of the new procedure, although the ability of the true party in interest to remain anonymous may make it attractive to some. Traditionally, the only way to challenge validity of a Japanese patent was by way of oppositions or invalidity trials. However, since the Japanese Supreme Court’s decision in Texas Instruments v. Fujitsu Ltd. (see our February 2002 Newsletter), the trial courts dealing with infringement actions have become increasingly willing to consider the validity of the patent in suit as well as whether it is infringed.