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Judge Robinson grants-in-part plaintiff’s motion to strike finding affirmative defense of invalidity inappropriate due to assignor estoppel

In Juniper Networks, Inc. v. Palo Alto Networks, Inc., C.A. No. 11-1258-SLR (D. Del. Aug. 2, 2012), Judge Robinson granted-in-part plaintiff’s motion to strike defendant’s affirmative defense of invalidity finding that the doctrine of assignor estoppel barred such a defense as to one of the patents-in-suit. Plaintiff argued that the inventors of the patents-in-suit were issued the patents while employed by plaintiff. Id. at 2-3. They subsequently left plaintiff to start another company (the defendant) and brought to defendant “the very same technology that they had previously developed and then assigned to [plaintiff] during their employment.” Id. at 3. Defendant disputed these facts arguing, among other things, that the inventors were not officers or founders of defendant. Id. at 2.

Judge Robinson noted that the Federal Circuit “reaffirmed the existence of the doctrine of assignor estoppel” in Diamond Scientific Co. v. Ambico, Inc., 848 F.2d 1220 (Fed. Cir. 1988). In Diamond, the Federal Circuit explained that assignor estoppel “is an equitable doctrine that prevents one who assigned the rights to a patent (or patent application)[, or other parties in privity with the assignor,] from later contending that what was assigned was a nullity” Id. at 4 (quoting Diamond, 848 F.2d 1224).

As to four of the patents-in-suit, Judge Robinson denied plaintiff’s motion because the issue of privity between the inventors and defendant could not be determined at “the pleadings stage” and that summary judgment was a “more appropriate venue[.]” Id. at 8-9. “Because the determination of privity . . . with respect to these four patents is a fact-sensitive inquiry that must be resolved outside the pleadings, and given the standard of review applicable to motions to strike, the court denies plaintiff’s motion at this time.” Id. at 9. Judge Robinson similarly denied plaintiff’s motion as to the fifth patent-in-suit because only one of the two inventors assigned his rights to plaintiff, which would require plaintiff to prove assignment by other means. Id. at 9-10. But, as to the sixth patent-in-suit, the sole inventor indisputably assigned the patent to plaintiff and he acknowledged being a founder of defendant, thereby establishing privity. Judge Robinson, therefore, granted plaintiff’s motion striking defendant’s invalidity defense as to that patent. Id. at 10.


Juniper Networks, Inc. v. Palo Alto Networks, Inc., C.A. No. 11-1258-SLR (D. Del. Aug. 2, 2012)

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