(Bench Opinion)

NOTE: Where it is feasible, a syllabus (headnote) will be released, as is being done in connection with this case, at the time the opinion is issued. The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience of the reader. See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.

SUPREME COURT OF THE UNITED STATES

Syllabus

WARNER-JENKINSON CO., INC. v. HILTON DAVIS CHEMICAL CO.

certiorari to the united states court of appeals for the federal circuit

No. 95–728. Argued October 15, 1996—Decided March 3, 1997

Petitioner and respondent both manufacture dyes from which impurities must be removed. Respondent's "'746 patent," which issued in 1985, discloses an improved purification process involving the "ultrafiltration" of dye through a porous membrane at pH levels between 6.0 and 9.0. The inventors so limited their claim's pH element during patent prosecution after the patent examiner objected because of a perceived overlap with the earlier "Booth" patent, which disclosed an ultrafiltration process operating at a pH above 9.0. In 1986, petitioner developed its own ultrafiltration process, which operated at a pH level of 5.0. Respondent sued for infringement of the '746 patent, relying solely on the "doctrine of equivalents," under which a product or process that does not literally infringe upon the express terms of a patent claim may nonetheless be found to infringe if there is "equivalence" between the elements of the accused product or process and the claimed elements of the patented invention. Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U. S. 605, 609. Over petitioner's objections that this is an equitable doctrine and is to be applied by the court, the equivalence issue was included among those sent to the jury, which found, inter alia, that petitioner infringed upon the '746 patent. The District Court, among its rulings, entered a permanent injunction against petitioner. The en banc Federal Circuit affirmed, holding that the doctrine of equivalents continues to exist, that the question of equivalence is for the jury to decide, and that the jury had substantial evidence from which to conclude that petitioner's process was not substantially different from the process disclosed in the '746 patent.

Held:

1. The Court adheres to the doctrine of equivalents. Pp. 4–10.

(a) In Graver Tank, supra, at 609, the Court, inter alia, described some of the considerations that go into applying the doctrine, such as the patent's context, the prior art, and the particular circumstances of the case, including the purpose for which an ingredient is used in the patent, the qualities it has when combined with the other ingredients, the function it is intended to perform, and whether persons reasonably skilled in the art would have known of the interchangeability of an ingredient not contained in the patent with one that was. Pp. 4–5.

(b) This Court rejects petitioner's primary argument, that the doctrine of equivalents, as set out in Graver Tank in 1950, is inconsistent with, and thus did not survive, particular aspects of Congress' 1952 revision of the Patent Act, 35 U. S. C. §100 et seq. Petitioner's first three arguments in this regard—that the doctrine (1) is inconsistent with §112's requirement that a patentee specifically "claim" the covered invention, (2) circumvents the patent reissue process under §§251–252, and (3) is inconsistent with the primacy of the Patent and Trademark Office (PTO) in setting a patent's scope—were made in Graver Tank, supra, at 613–615, and n. 3, in the context of the 1870 Patent Act, and failed to command a majority. The 1952 Act is not materially different from the 1870 Act with regard to these matters. Also unpersuasive is petitioner's fourth argument, that the doctrine of equivalents was implicitly rejected as a general matter by Congress' specific and limited inclusion of it in §112, ¶6. This new provision was enacted as a targeted cure in response to Halliburton Oil Well Cementing Co. v. Walker, 329 U. S. 1, 8, and thereby to allow so-called "means" claims describing an element of an invention by the result accomplished or the function served. Moreover, the statutory reference to "equivalents" appears to be no more than a prophylactic against potential side effects of that cure, i.e., an attempt to limit the application of the broad literal language of "means" claims to those means that are "equivalent" to the actual means shown in the patent specification. Pp. 6–9.

(c) The determination of equivalence should be applied as an objective inquiry on an element-by-element basis. The Court is concerned that the doctrine, as it has come to be broadly applied since Graver Tank, conflicts with the Court's numerous holdings that a patent may not be enlarged beyond the scope of its claims. The way to reconcile the two lines of authority is to apply the doctrine to each of the individual elements of a claim, rather than to the accused product or process as a whole. Doing so will preserve some meaning for each of a claim's elements, all of which are deemed material to defining the invention's scope. So long as the doctrine does not encroach beyond these limits, or beyond related limits discussed in the Court's opinion, infra, at 11–15, 20, n. 8, and 21–22, it will not vitiate the central functions of patent claims to define the invention and to notify the public of the patent's scope. Pp. 9–10.

(d) Petitioner is correct that Graver Tank did not supersede the well-established limitation on the doctrine of equivalents known as "prosecution history estoppel," whereby a surrender of subject matter during patent prosecution may preclude recapturing any part of that subject matter, even if it is equivalent to the matter expressly claimed. But petitioner reaches too far in arguing that any such surrender establishes a bright line beyond which no equivalents may be claimed, and that the reason for an amendment during patent prosecution is therefore irrelevant to any subsequent estoppel. There are a variety of reasons why the PTO may request a change in claim language, and if the patent-holder demonstrates that an amendment had a purpose unrelated to patentability, a court must consider that purpose in order to decide whether an estoppel is precluded. Where the patent-holder is unable to establish such a purpose, the court should presume that the purpose behind the required amendment is such that prosecution history estoppel would apply. Here, it is undisputed that the upper limit of 9.0 pH was added to '746 patent in order to distinguish the Booth patent, but the record before this Court does not reveal the reason for adding the lower 6.0 pH limit. It is therefore impossible to tell whether the latter reason could properly avoid an estoppel. Pp. 10–15.

(e) The Court rejects petitioner's argument that Graver Tank requires judicial exploration of the intent of the alleged infringer or a case's other equities before allowing application of the doctrine of equivalents. Although Graver Tank certainly leaves room for the inclusion of intent-based elements in the doctrine, the Court does not read the case as requiring proof of intent. The better view, and the one consistent with Graver Tank's predecessors, see e.g., Winans v. Denmead, 15 How. 330, 343, and the objective approach to infringement, is that intent plays no role in the doctrine's application. Pp. 15–18.

(f) The Court also rejects petitioner's proposal that in order to minimize conflict with the notice function of patent claims, the doctrine of equivalents should be limited to equivalents that are disclosed within the patent itself. Insofar as the question under the doctrine is whether an accused element is equivalent to a claimed element, the proper time for evaluating equivalency—and knowledge of inter changeability between elements—is at the time of infringement, not at the time the patent was issued. P. 18.

(g) The Court declines to consider whether application of the doctrine of equivalents is a task for the judge or for the jury, since resolution of that question is not necessary to answer the question here presented. Pp. 19–20.

(h) In the Court's view, the particular linguistic framework used to determine "equivalence," whether the so-called "triple identity" test or the "insubstantial differences" test, is less important than whether the test is probative of the essential inquiry: Does the accused product or process contain elements identical or equivalent to each claimed element of the patented invention? Different linguistic frameworks may be more suitable to different cases, depending on their particular facts. The Court leaves it to the Federal Circuit's sound judgment in this area of its special expertise to refine the formulation of the test for equivalence in the orderly course of case-by-case determinations. Pp. 21–22.

2. Because the Federal Circuit did not consider all of the requirements of the doctrine of equivalents as described by the Court in this case, particularly as related to prosecution history estoppel and the preservation of some meaning for each element in a claim, further proceedings are necessary. P. 22.

62 F. 3d 1512, reversed and remanded.

Thomas, J., delivered the opinion for unamimous Court. Ginsburg, J., filed a concurring opinion, in which Kennedy, J., joined.