Assignor Estoppel

  • Assignor Estoppel Bars Patent’s Assignor Or Privity From Challenging Patent Validity: Equitable remedy barring assignor of patent, or one in privity with assignor, from challenging validity of patent if sued for infringement. Mag Aerospace (Fed. Cir. 03/23/16) (aff’g Summ. J. that defendant estopped because it hired a named inventor on asserted patent to help develop the accused system, despite that employee’s negligible financial interest in the defendant); Mentor Graphics (Fed. Cir. 03/16/17) (aff’g application of assignor estoppel; Fed. Cir. already rejected argument that Lear (U.S. 06/16/1969) abolished assignor estoppel), rehearing denied (Fed. Cir. 09/01/17) (Moore, J., concurring op. (2 judges) (Lear does not overrule Westinghouse; “The question of privity and the extent to which assignor estoppel ought to prohibit a future employer of the inventor/assignor from challenging the validity of the patent is an interesting one not raised by the parties on appeal in this case”)), CVSG (U.S. 04/23/2018); see generally Shamrock Tech. (Fed. Cir. 05/04/90) (discussing equitable factors for privity determination, and applying assignor estoppel to inequitable conduct).
  • Assignor Estoppel Applies Even To Claims Broader In Scope Than Claims Pending At Time Of Assignment: Broadening of claims does not negate assignor estoppel, but estopped party may introduce evidence of prior art to narrow the scope of claim “so as to bring its accused product ‘outside the scope of’” of the claim. Hologic (Fed. Cir. 04/22/20) (aff’g application of assignor estoppel).
  • Assignor Estoppel Does Not Apply To PTAB Proceedings: Arista (Fed. Cir. 11/09/18) (assignor estoppel does not apply to IPR proceedings: “§ 311(a) unambiguously leaves no room for assignor estoppel in the IPR context, given that the statute allows any person “who is not the owner of a patent” to file an IPR,” and the statute does not provide that all equitable defenses apply (unlike ITC proceedings)).
  • Assignor Estoppel Does Not Bar Assertion Of Issue Preclusion Against Patent Owner Who Lost Invalidity Or Patentability Challenge In Another Proceeding (E.g., In PTAB): Hologic (Fed. Cir. 04/22/20) (aff’g that although assignor estoppel barred invalidity defense against continuation patents (whose applications were assigned by inventor/defendant’s principal) despite claims being held unpatentable by PTAB and Fed. Cir., it did not bar assertion of issue preclusion that claims were void ab initio, thus avoiding an injunction and monetary relief).

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