Center for Advanced Study & Research on Intellectual Property


CASRIP Newsletter - Fall 1995, Volume 2, Issue 3


Federal Circuit Confirms "Substantial Difference" Test and Jury Trial Right for Doctrine of Equivalents - The 1995 Hilton Davis Chemical Co. en banc decision.

On August 8, 1995, the long-awaited en banc decision on the doctrine of equivalents, Hilton Davis Chemical Co. v. Warner- Jenkinson Co., was handed down by the Federal Circuit. Contrary to the expectations of many, the court, speaking through a majority opinion for seven of the twelve participating judges, did not make major changes in the doctrine. Noting that the case "presents an opportunity to restate--not to revise--the test for infringement under the doctrine of equivalents," it relied primarily on the 1950 Graver Tank decision, which is the Supreme Court's last pronouncement on the doctrine, to declare that (1) the ultimate test for nonliteral infringement is whether the differences between the claimed and accused structure are "substantial"and (2) equivalency is a factual issue to which the right to jury trial attaches.

The close vote and tone of the concurring opinion by Judge Newman and lengthy dissenting opinions, by Judges Plager, Lourie and Nies separately, suggest that the equivalency doctrine's status is far from settled. Of the seven majority votes, one is by a senior judge who will not participate actively in future cases. The court's newest judge (Bryson) did not participate. In concurring, Judge Newman thoughtfully suggested that the doctrine of equivalents needs further study and evaluation and should, perhaps, be revised by legislative enactment.

Hilton Davis Chemical's holding that equivalency is a fact question for jury resolution comes on the heels of Markman's holding that claim interpretation is a legal question for judicial resolution. The sharpness of this distinction can only confound those who see claim interpretation and claim application (equivalency) as opposing ends of a single continuum, an ultimate, policy-based decision on what scope of protection a patented invention should be given.

The following outline encapsulates the major points made in the majority opinion.

A. SUBSTANTIALITY AS ULTIMATE QUESTION. "[T]he substantiality of the differences between the claimed and accused products or processes is the ultimate question under the doctrine of equivalents . . ."

B. FUNCTION-WAY-RESULT TEST AND OTHER FACTORS. "[A] finding of infringement under the doctrine of equivalents requires proof of insubstantial differences between the claimed and accused products or processes."

(i) "Often the function-way-result test will suffice to show the extent of the differences. In such cases, the parties will understandably focus on the evidence of function, way, and result, and the fact-finder will apply the doctrine based on that evidence."

(ii) COPYING AND DESIGNING AROUND. "Other factors, however, such as evidence of copying or designing around, may also inform the test for infringement under the doctrine of equivalents."

(iii) OBJECTIVE TEST--SUBJECTIVE CONCLUSIONS. "In either event, the vantage point of one of ordinary skill in the relevant art provides the perspective for assessing the substantiality of the differences. . . . The test is objective, with proof of the substantiality of the differences resting on objective evidence rather than unexplained subjective conclusions, whether offered by an expert witness or otherwise."

(iv) KNOWN INTERCHANGEABILITY. "The known interchangeability of the accused and claimed elements is potent evidence that one of ordinary skill in the relevant art would have considered the change insubstantial. Without such evidence, the patentee will need other objective technological evidence demonstrating that the substitute nevertheless represents a change that the ordinary artisan would have considered insubstantial at the time of infringement."

(v) "Limiting the range of potentially infringing substitutions to those known at the time of the patent's issuance would undermine the doctrine, denying patent owners protection of the substance of their inventions against new forms of infringement."

(vi) "No judge can anticipate whether such other factors will arise in a given case. Instead, the presence of such factors will depend on the way the parties frame their arguments. Neither the Supreme Court nor this court limits the types of evidence that either party may proffer in support of a factor it considers probative of infringement under the doctrine."

(vii) "The trial judge, however, has a duty to decide whether the proffered evidence is relevant. This duty to assess relevance is no different in a doctrine of equivalents case than in any other type of case."

(viii) "Relevance will be self-evident to the judge in a case tried to the bench. In a jury trial, however, the judge must admit only relevant evidence, and instruct the jury to consider only the admitted evidence in reaching its decision."

C. INDEPENDENT DEVELOPMENT. Evidence of independent development "is not directly relevant to infringement under the doctrine of equivalents" but "is highly relevant . . . to refute a patent owner's contention that the doctrine of equivalents applies because the accused infringer copied, that is, intentionally appropriated the substance of the claimed invention. . . ."

D. STRICT LIABILITY OFFENSE. "[N]either evidence of copying, independent development, nor `designing around' owes its relevance in a doctrine of equivalents analysis to the state of mind of the accused infringer. Infringement is, and should remain, a strict liability offense."

E. FACT ISSUE FOR JURY. "[I]nfringement under the doctrine of equivalents is an issue of fact to be submitted to the jury in a jury trial with proper instructions, and to be decided by the judge in a bench trial."

F. DISCRETION--EQUITY. "The trial judge does not have discretion to choose whether to apply the doctrine of equivalents when the record shows no literal infringement." "The doctrine of equivalents has no equitable or subjective component. . . . London . . . and Charles Greiner . . . reaffirm that the Graver Tank objective criteria, as limited by prosecution history and prior art, confine the range of equivalents. These cases do not condition effective patent protection on proof of bad faith."

The facts in Hilton-Davis presented a prototypical patent claim scope problem: the patent claim contained a limitation (a minimum value in a range) that turned out to be neither necessary to distinguish the prior art nor to establish the invention's operability. The patent in suit ('746) concerned a process for removing impurities from food and drug dyes (Red Dye #40 and Yellow Dye #6). The patent discloses an "ultrafiltration" process that "filters impure dye solution through a membrane at certain pressures, pHs, and pore diameters. Impurities, but not dye molecules, pass through the membrane, leaving a high purity dye product." The claim required that an aqueous solution be "at a pH from approximately 6.0 to 9.0." "The inventors added the phrase `at a pH from approximately 6.0 to 9.0' during prosecution to distinguish [the Booth patent]. The Booth patent discloses an ultrafiltration process that, among other differences from the '746 process, operates at a pH above 9 and preferably between 11 and 13." The accused process used a lower pH of 5.0.

At trial, the jury found infringement. The court found the verdict supported by substantial evidence.

"The claimed pH limitation prevents damage to the membrane and produces a neutral final dye product. Dr. Cook, one of the inventors, testified that a pH of 5 would have the same effect as a pH of 6, as would any pH above 2. Even Warner-Jenkinson's expert agreed that Hilton Davis' process would operate at a pH of 5. The record contains substantial evidence that one of skill in the art would know that performing ultrafiltration at a pH of 5 would allow the membrane to perform the same function, in an equivalent way, to achieve the same result as at a pH of approximately 6 to 9."

Does it make sense to say that a process with an acqueous solution of 5.0 pH (the accused process) is "substantially the same" as one with a pH of "approximately 6.0" (the patent claim)? If "substantial" means of "any substance", that is, actual or real as opposed to merely verbal, the difference, at first blush, seems indisputably substantial. But, as an aid to analysis, consider that there are at least three ways to characterize the problem. First, most narrowly, one could look only at whether 6.0 to 5.0, considered in isolation, is substantial. So viewed, the chemical change seems clearly substantial or significant. (The court recognized that the pH scale is logarithmic so that a 1.0 scale difference is a 10 times difference.) Second, one could look to the properly-interpreted claim language "as a whole". So viewed, the question becomes a bit closer. The claim stated "approximately" 6.0, alerting the reader that the quantity limits were not to be taken as precise. It also linked the quantity limitation to a functional result: "subjecting an aqueous solution . . . to ultrafiltration through a membrane . . . at a pH from approximately 6.0 to 9.0, to thereby cause separation of said impurities from said dye." Thus, the reader is told that the specified pH level need only approximate the 6.0 to 9.0 range so as to achieve the specified result. If, as is the settled law, the claim is interpreted in view of the prosecution history, which suggested that only the upper end of the 6.0 to 9.0 range was critical to distinguish the prior art, the case for finding the difference insubstantial (or even nonexistent) grows stronger. But, washed in critical acid, it remains difficult to fairly characterize such a physical change as truly "insubstantial."

Finally, one could unhinge the comparison from the claim language, recognizing that there are situations in which an informed reader, attempting fairly to determine what the invention is from the patent disclosure and the patent's prosecution history, will recognize that the claim only imperfectly expresses the invention and will perceive that it extends to embodiments that do not literally meet the 6.0 minimum pH. It is only with this view of the comparison that one can truly say that the difference is insubstantial.

- Donald S. Chisum

Last updated 4/27/2012