Mycogen Plant Science, Inc. v. Monsanto Co.

Mycogen Plant Science, Inc. (Mycogen) (plaintiff) owned three related United States patents: United States Patent No. 5,567,600 (the 600 patent), United States Patent No. 5,567,862 (the 862 patent), and United States Patent No. 5,380,831 (the 831 patent). The 600 and 862 patents were child patents of the 831 patent. All three patents had identical titles, nearly identical specifications, and disclosed similar claims. The 600 and 862 patents were the subject of an infringement suit between Mycogen and Monsanto Co. (defendant). In that case (Delaware I), the issues of claim construction and patent invalidity were fully litigated and were essential to the ultimate jury verdict of invalidity of the 600 and 862 patents. The jury found the patents invalid due to prior invention. This resolution included a finding that Monsanto was the first to reduce to practice the four-step invention of the 600 patent. On appeal, the claim construction and jury verdict were affirmed. Mycogen sued Monsanto in a separate action in federal court for infringement of the 831 patent, which claimed a two-step invention. The four steps of the 600 patent included the two steps of the 831 patent. The district court granted summary judgment of invalidity, relying in part on the conclusion that the doctrine of collateral estoppel required the district court to adopt Delaware I’s claim construction and its determination that Monsanto was first to reduce the four-step invention to practice. Mycogen appealed.