The rule of law in patent cases was to allow a patentee another suit even if he lost a first suit to uphold his patent; Triplett v. Lowell 297 U.S. 638 (1936). The lower courts allowed Foundation (P) to maintain a second action after losing its first. P owned a patent for a radio and television antenna. Its patent was held invalid in its first suit. P then sued Blonder (D) for infringement on the same patent. D asserted collateral estoppel. The Supreme Court granted certiorari.