In Graver Tank, the Linde Air Products Co. sued Graver Tank & Manufacturing Co., among others, for welding compositions or fluxes. The Supreme Court found that the substitution of one element for another resulted in a change that avoided literal infringement but that the changes were “colorable only.” The Graver Tank case essentially provided a way to construe the claims to apply beyond the literal language of the claims and can be applied to both the patentee and the defendant.
After Graver Tank, the Supreme Court did not feel the need to rule on the doctrine of equivalents until 1997, when a dispute in which Hilton Davis Chemical Co. sued Warner-Jenkinson Co. over an ultrafiltration process landed on its docket. Hilton Davis sued Warner-Jenkinson in district court relying solely on the doctrine of equivalents. Warner-Jenkinson tried to argue that the doctrine was an equitable doctrine and is to be applied by the court, but it was sent to the jury. In addition, during the prosecution of the patent at the center of the suit, Hilton Davis amended the claims to adjust the range of pH used in the claims. Warner-Jenkinson also raised this issue during trial and tried to assert prosecution history estoppel. The U.S. Court of Appeals for the Federal Circuit affirmed the application and validity of the doctrine-of-equivalents arguments, and the case went before the Supreme Court. The Supreme Court not only affirmed the validity of the doctrine-of-equivalents arguments; it went on to expand the applicability of the doctrine beyond the contents of the patent application. Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17, 177 S. Ct. 1040, 137 L. Ed. 2d 146, 41 U.S.P.Q. 1865 (1997). At this point, the doctrine was alive and well.
However, five years later, the Supreme Court then restricted the application of the doctrine of equivalents in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., 535 U.S. 722, 122 S. Ct. 1831, L. Ed. 2d 944, 62 U.S.P.Q.2d 1705 (2002). This began the doctrine’s slow slide into oblivion, or so it seemed. The Supreme Court found that any amendment made during prosecution history may apply to any claim amendment made, whether for formalities or to overcome prior art, and the patentee has the burden to prove that the amendment did not surrender the equivalent being asserted.
Following this decision, one could almost watch as the doctrine became sickly and the number of doctrine-of-equivalents cases presented to the Federal Circuit started to fall off. The number of cases has fallen off dramatically, and an informal survey of various commentators seems to have indicated that the doctrine had all but died, mostly because of prosecution history estoppel. See, for example, Pharma Tech Solutions, Inc. v. Lifescan, Inc., 942 F.3d 1372 (Fed. Cir. 2019), and Amgen, Inc. v. Sandoz, Inc., 923 F.3d 1023 (Fed. Cir. 2019). The doctrine seemed to lie on its deathbed, just waiting for its final gasp.
However, by some miracle tonic, or a renewed interest in life, the doctrine of equivalents gathered itself up and came to play in the Western District of Texas. It asserted its presence with authority, to the tune of $675 million.
VLSI continues to pursue Intel and recently made a motion to move its other cases to the Western District of Texas, and there will undoubtedly be appeals on the verdict above as well as those to come. We shall see if the doctrine of equivalents will survive or may be finally laid to rest.