Blonder-Tongue Laboratories, Inc. v. University of Illinois Foundation

Background

A university foundation owned two antenna patents, including the Isbell patent, and sued manufacturers for infringement. In one earlier case the Eighth Circuit held the Isbell patent invalid. In a later suit the Seventh Circuit found the same patent valid and infringed against Blonder-Tongue Laboratories (B-T), creating a direct conflict between circuits and prompting review by the Court.

Reasoning

The central question was whether a patentee can relitigate patent validity against new defendants after a federal court already declared the patent invalid. The Court concluded that the old Triplett rule, which barred an accused infringer from invoking a prior invalidity ruling, should be overruled insofar as it prevented a defendant from pleading estoppel (a defense that stops relitigation of an issue). The Court explained that many courts had already eroded the mutuality rule, patent suits are costly, and fairness requires that trial courts decide whether the patentee had a full and fair chance earlier. The Court vacated the appeals judgment and remanded so B-T could amend to assert estoppel and the Foundation could supplement the record.

Real world impact

Going forward, defendants in patent cases may block repeat suits when a patent was already judged invalid, but courts must still evaluate whether the patentee had a fair first opportunity to litigate. This decision does not resolve the patent’s validity on the merits; it simply permits a defendant to raise an estoppel defense and requires further district-court proceedings to apply that rule here.