Hilton Davis Chemical Co. sued Warner-Jenkinson Co., Inc. for infringement of its U.S. Patent 4,560,746 (the '746 patent). The '746 patent claims a process for purification of dyes using ultrafiltration. The elements of the main claim that were in issue were the pore diameter of the filtration membrane used (5-15 angstroms); the hydrostatic pressure used during filtration (approximately 200 to 400 p.s.i.g.) and the pH at which the ultrafiltration took place (from approximately 6.0 to 9.0). The alleged infringing process was found to operate at pressures somewhere in a range of 200 to nearly 500 p.s.i.g. and a pH of 5. There was testimony that the pore diameter of the filters used by the alleged infringer was 5 to 15 Angstroms. At trial, although Warner-Jenkinson's ultrafiltration process to purify dyes was not found to infringe the '746 patent literally, infringement under the doctrine of equivalents was found. The Court of Appeals for the Federal Circuit in a 7-5 en banc decision affirmed the decision of the trial court of infringement under the doctrine of equivalents.
It was expected that this decision would clarify or set new guidelines on the doctrine of equivalents because the Federal Circuit had requested the following questions be briefed by the parties:
1) Does a finding of infringement under the doctrine of equivalents require anything in addition to proof of the facts that there are the same or substantially the same (a) function, (b) way, and (c) result, the so-called triple identity test of Graver Tank [& Manufacturing Co.] v. Linde Air Products., and cases relied on therein? If yes, what?
2) Is the issue of infringement under the doctrine of equivalents an equitable remedy to be decided by the court, or is it, like literal infringement, an issue of fact to be submitted to the jury in a jury case?
3) Is application of the doctrine of equivalents by the trial court to find infringement of the patentee's right to exclude, when there is no literal infringement of the claim, discretionary in accordance with the circumstances of the case?
2) Is the issue of infringement under the doctrine of equivalents an equitable remedy to be decided by the court, or is it, like literal infringement, an issue of fact to be submitted to the jury in a jury case?
3) Is application of the doctrine of equivalents by the trial court to find infringement of the patentee's right to exclude, when there is no literal infringement of the claim, discretionary in accordance with the circumstances of the case?
In fact, rather than clarify or set new guidelines, the majority stated that the case presents "an opportunity to restate --not to revise -- the test for infringement under the doctrine of equivalents" and the majority opinion confined itself to holding that "the application of the doctrine of equivalents rests on the substantiality of the differences between the claimed and accused products or processes, assessed according to an objective standard."
The Federal Circuit's comments on whether an alleged infringement is substantially the same as what is claimed are of interest. The Federal Circuit in response to the first question stated "infringement under the doctrine of equivalents requires proof of insubstantial differences between the claimed and accused products or processes." The determination of whether there is infringement under the doctrine of equivalents is not limited to the function-way-result test of Graver Tank and when there is other evidence relevant to the substantiality of the differences between the claimed and accused products or processes, this evidence must be considered by the fact-finder. This evidence could include whether those skilled in the art were aware of the interchangeability of the elements, evidence of copying, independent development, and designing around on the part of the alleged infringer.
In reply to the second and third questions, the Federal Circuit stated that infringement under the doctrine of equivalents is a question of fact to be submitted to a jury in a jury trial and to be decided by the judge in a bench trial, and that the "trial judge does not have discretion to choose whether to apply the doctrine of equivalents when the record shows no literal infringement" (i.e., the application of the doctrine was a matter of law, not of equity).
The majority opinion was criticized both in the concurring and dissenting opinions because it failed to consider wider issues such as the right of the public to know what was protected by a patent claim or to impose constraints on the doctrine of equivalents which some consider is used routinely by patentees to enlarge the scope of their claims and cause uncertainty among their competitors.
November 1995 Index