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Thursday, August 5, 2010

Prosecution History Estoppel Not So Clear

The CAFC's decision in Intervet v. Merial provides a useful discussion of prosecution history estoppel in overturning the District Court decision that Such an estoppel precluded arguing that an equivalent found in the patent examples should be within the scope of the claims.  In particular, the Court stated:


Whether prosecution history estoppel applies to a particular argument, and thus whether the doctrine of equivalents is available for a particular claim limitation, is a question of law. Bai v. L & L Wings, Inc., 160 F.3d 1350, 1354 (Fed. Cir. 1998); Cybor Corp. v. FAS Techs., Inc., 138 F.3d 1448, 1460 (Fed. Cir. 1998) (en banc). Where an amendment narrows the scope of the claims, and that amendment is adopted for a substantial reason related to patentability, the amendment gives rise to a presumption of surrender for all equivalents that reside in "the territory between the original claim and the amended claim." Festo Corp. v Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 740 (2002) (Festo VIII). This presumption can be overcome by showing that "at the time of the amendment one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent." Id. at 741. One way to make this showing is to demonstrate that "the rationale underlying the narrowing amendment bore no more than a tangential relation to the equivalent in question." Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 344 F.3d 1359, 1368 (Fed. Cir. 2003) (en banc) (Festo IX). Although there is no hard-and-fast test for what is and what is not a tangential relation, it is clear that an amendment made to avoid prior art that contains the equivalent in question is not tangential. See Pioneer Magnetics, Inc. v. Micro Linear Corp., 330 F.3d 1352, 1357 (Fed. Cir. 2003).
The applicability of prosecution history estoppel does not completely bar the benefit of the doctrine of equivalents from all litigation related to the amended claim. See Festo VIII, 535 U.S. at 73738 ("There is no reason why a narrowing amendment should be deemed to relinquish equivalents . . . beyond a fair interpretation of what was surrendered.") The scope of the estoppel must fit the nature of the narrowing amendment. A district court must look to the specifics of the amendment and the rejection that provoked the amendment to determine whether estoppel precludes the particular doctrine of equivalents argument being made.
      Bottom line is that prosecution history estoppel may not be the absolute bar that it has been thought to be since Festo VIII.