The Court of Appeals for the Federal Circuit announced in Hilton Davis Chemical Co. v. Warner-Jenkinson Co., Inc., No. 93-1088, slip. op. (Fed. Cir. August 8, 1995)(en banc) that the doctrine of equivalents is alive and well and is what the Supreme Court said it was forty-five years ago in Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605 (1950), although the Federal Circuit now gives it a somewhat different analytical treatment. The Court, in a 7 5 en banc, per curiam decision, clearly held that application of the doctrine of equivalents is available to all patent owners as a matter of law. However, five dissenting judges did not close the door on the possibility that in the future a patent owner will may be required to establish a favorable threshold equity before he can invoke the doctrine of equivalents.
The claims of Hilton Davis' U.S. Patent No. 4,560,746 recite a dye purifying process including:
"ultrafiltration through a membrane having a nominal pore diameter of 5-15 Angstroms under a hydrostatic pressure of approximately 200 to 400 p.s.i.g., at a pH from approximately 6.0 to 9.0 . . .."
Although "at a pH from approximately 6.0 to 9.0" was added by amendment to distinguish the prior art, the Court held that this amendment did not preclude application of the doctrine of equivalents for a pH below 6 because the prior art disclosed only a pH range over 9.0.
The evidence showed that Warner-Jenkinson used a process with a membrane having a pore diameter of 5-15 Angstroms operated at pressures from 200 to nearly 500 p.s.i.g. and a pH of 5. On this evidence and applying the familiar "substantially the same" function-way-result test of Graver Tank, the jury held that Warner-Jenkinson's process using a pH of 5 infringed the claims of the '746 patent under the doctrine of equivalents.
Warner-Jenkinson appealed. After a three-judge panel of the Court initially heard oral argument on July 9, 1993, the Court, en banc, ordered a rehearing, and asked for supplementary briefing on three issues. The issues posed by the Court en banc are: (1) whether infringement under the doctrine of equivalents requires anything in addition to the function-way-result test of Graver Tank; (2) whether infringement under the doctrine of equivalents is an equitable remedy to be decided by the court or an issue of fact to be submitted to the jury in a jury case; and (3) whether or not the court has discretion to apply the doctrine of equivalents. The rehearing on these three issues was held on March 7, 1994.
The Court's opinion initially states that "This case presents an opportunity to restate--not to revise--the test for infringement under the doctrine of equivalents." The opinion focuses on a frequently overlooked other holding in Graver Tank that "insubstantial differences" are "the necessary predicate" to find infringement under the doctrine of equivalents.
In answering Question One, the Court interpreted Graver Tank as establishing that the ultimate inquiry under the doctrine of equivalents is an objective assessment of the substantiality of the differences between the claimed and accused products or processes, and that application of the function-way-result test is but one way of determining the substantiality of such differences.
The Court acknowledged that similarity of function, way and result often discloses the substantiality of the differences, and thus has often been used to describe the doctrine of equivalents. However, the Court stated that the function-way-result test does not necessarily end the inquiry. That is, evidence going to the substantiality of the differences, beyond function, way and result, also may be considered by the fact finder.
In particular, the Court noted that interchangeability of the accused and claimed elements, as recognized by those of ordinary skill in the relevant art, judged at the time of the infringement (not at the time of the invention), is "potent evidence" that the change is insubstantial and thus infringing under the doctrine of equivalents.
The Court also stated that evidence of designing around the patent claims provides an inference that substantial changes have been designed into the new product to avoid infringement, and thus weighs against finding infringement under the doctrine of equivalents.
The Court further stated, conversely, that evidence of copying provides an inference that the differences are only insubstantial and thus infringing. "Evidence of culpable conduct, however, is not a prerequisite nor necessary for application of the doctrine." The "subjective awareness or intent of the accused infringer" is not a required element of the doctrine of equivalents.
The Court additionally observed that evidence of independent development is not directly relevant to the question of infringement under the doctrine of equivalents. However, evidence of independent development is highly relevant to refute an allegation of copying. And the Court interpreted Graver Tank as further holding that where the record lacks evidence of independent development there can be an inference of copying.
In answering Question Two, and again relying on Graver Tank, the Court held that infringement under the doctrine of equivalents is an issue of fact to be submitted to the jury in a jury trial.
Warner-Jenkinson contended that its independent development precluded application of the doctrine of equivalents. The Court dismissed Warner-Jenkinson's equitable defense to application of the doctrine of equivalents holding that the doctrine has no equitable or subjective component.
Further, the Court reasoned that because the doctrine of equivalents is legal, not equitable, it cannot be applied at the court's discretion. Citing Graver Tank and prior Supreme Court precedent, the Court held that all patent owners are entitled in all cases to invoke the doctrine of equivalents, thus answering Question Three.
While ostensibly leaving the doctrine of equivalents unchanged, the majority opinion in Hilton Davis clearly signals a shifting in focus from the function-way-result test to a substantiality of the differences analysis. As a practical matter, because of the additional evidence, beyond the function-way-result test, which the Court expressly identified as being relevant for determining the substantiality of the differences, it will now be even more important than ever to consider the factors of interchangeability, copying, designing around and independent development when making decisions and taking actions relating to product and process development.