OCTOBER TERM, 1996
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:
(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
18
Syllabus
skilled in the art would have known of the interchangeability of
an ingredient not contained in the patent with one that was. Pp.
24-25.
(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. 25-28.
(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
30-34, 39, n. 8, and 39-40, 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. 28-30.
(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
19
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 the '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.
30-34.
(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. 34-36.
(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 interchangeability between elements-is at the time of
infringement, not at the time the patent was issued. P. 37.
(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. 37-39.
(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
20
Syllabus
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.39-40.
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. Pp. 40-41.
62 F.3d
1512, reversed and remanded.
THOMAS, J., delivered the opinion for a unanimous Court.
GINSBURG, J., filed a concurring opinion, in which KENNEDY, J.,
joined,
post, p. 41.
Richard G.
Taranto argued the cause for
petitioner. With him on the briefs were
H. Bartow Farr
III and
J. Robert Chambers.
Deputy Solicitor General Wallace argued the cause for the United
States as amicus curiae. With him on the brief were Solicitor
General Days, Assistant Attorney General Bingaman, Cornelia T. L.
Pillard, Nancy J. Linck, and Albin F. Drost.
David E. Schmit argued the cause and filed a brief for
respondent. *
*Briefs of
amici curiae urging reversal were filed for
Gateway Technologies, Inc., by
Richard Grant Lyon; for GHZ
Equipment Co. by
Ronald D. Maines and
Richard G.
Wilkins; for the Information Technology Industry Council et
al. by
Joel M. Freed, Jerrold J. Ganzfried,
John F.
Cooney, and
William D. Coston; for the
Intellectual Property Owners by
Carter G.
Phillips, Mark
E. Haddad, and
Joseph R. Guerra; for MCI
Telecommunications Corp. by
Paul M. Smith and
Nory
Miller; for Micron Separations, Inc., by
Steven M. Bauer
and
John J. Cotter; and for Seagate
Technology, Inc., et al. by
Carrie L. Walthour, Karl A. Limbach,
Deborah BaileyWells, and
Edward P. Heller III.
Briefs of
amici curiae urging affirmance were filed for
the Biotechnology Industry Organization by
Charles E.
Ludlam; for Chiron Corp. by
Donald S.
Chisum; for
the Dallas-Fort Worth Intellectual Property Law Association by
Lawrence J. Bassuk; for Litton Systems, Inc.,
by
Laurence
21
JUSTICE THOMAS delivered the opinion of the Court. Nearly 50
years ago, this Court in
Graver Tank &
Mfg.
Co. v.
Linde Air Products Co., 339 U. S. 605 (1950), set
out the modern contours of what is known in patent law as the
"doctrine of equivalents." Under this doctrine, 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.
Id., at 609. Petitioner, which was found to have infringed
upon respondent's patent under the doctrine of equivalents, invites
us to speak the death of that doctrine. We decline that invitation.
The significant disagreement within the Court of Appeals for the
Federal Circuit concerning the application of
Graver Tank
suggests, however, that the doctrine is not free from confusion. We
therefore will endeavor to clarify the proper scope of the
doctrine.
I
The essential facts of this case are few. Petitioner
Warner-Jenkinson Co. and respondent Hilton Davis Chemical Co.
manufacture dyes. Impurities in those dyes must be removed. Hilton
Davis holds United States Patent No. 4,560,746 ('746 patent), which
discloses an improved purification process involving
"ultrafiltration." The '746 process filters impure dye through a
porous membrane at certain
H. Tribe and Jonathan S. Massey; and for the Ohio State Bar
Association by Eugene P. Whetzel and Albert L. Bell.
Briefs of
amici curiae were filed for the American
Automobile Manufacturers Association by
D. Dennis Allegretti,
Phillip D. Brady, and
Andrew D. Koblenz; for the
American Intellectual Property Law Association by
Robert
J. Baechtold, Stevan J. Bosses, Nicholas M.
Cannella, Charles L. Gholz, and
Roger W Parkhurst; for
the Chemical Manufacturers Association by
Robert A. Armitage
and
Michael P. Walls; and for the Licensing Executive
Society (D. S. A. and Canada), Inc., by
Gayle Parker and
James W Gould.
22
pressures and pH levels,l resulting in a high purity dye
product.
The '746 patent issued in 1985. As relevant to this case, the
patent claims as its invention an improvement in the
ultrafiltration process as follows:
"In a process for the purification of a dye ... the improvement
which comprises: subjecting an aqueous solution ... to
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, to
thereby cause separation of said impurities from said dye .... "
App. 36-37 (emphasis added).
The inventors added the phrase "at a pH from approximately 6.0
to 9.0" during patent prosecution. At a minimum, this phrase was
added to distinguish a previous patent (the "Booth" patent) that
disclosed an ultrafiltration process operating at a pH above 9.0.
The parties disagree as to why the low-end pH limit of 6.0 was
included as part of the claim.2
1 The pH, or power (exponent) of Hydrogen, of a solution is a
measure of its acidity or alkalinity. A pH of 7.0 is neutral; a pH
below 7.0 is acidic; and a pH above 7.0 is alkaline. Although
measurement of pH is on a logarithmic scale, with each whole number
difference representing a tenfold difference in acidity, the
practical significance of any such difference will often depend on
the context. Pure water, for example, has a neutral pH of 7.0,
whereas carbonated water has an acidic pH of 3.0, and concentrated
hydrochloric acid has a pH approaching 0.0. On the other end of the
scale, milk of magnesia has a pH of 10.0, whereas household ammonia
has a pH of 11.9. 21 Encyclopedia Americana 844 (Int'l ed.
1990).
2 Petitioner contends that the lower limit was added because
below a pH of 6.0 the patented process created "foaming" problems
in the plant and because the process was not shown to work below
that pH level. Brief for Petitioner 4, n. 5,37, n. 28. Respondent
counters that the process was successfully tested to pH levels as
low as 2.2 with no effect on the process because of foaming, but
offers no particular explanation as to why the lower level of 6.0
pH was selected. Brief for Respondent 34, n. 34.
23
In 1986, Warner-Jenkinson developed an ultrafiltration process
that operated with membrane pore diameters assumed to be 5-15
Angstroms, at pressures of 200 to nearly 500 p. s. i. g., and at a
pH of 5.0. Warner-Jenkinson did not learn of the '746 patent until
after it had begun commercial use of its ultrafiltration process.
Hilton Davis eventually learned of Warner-Jenkinson's use of
ultrafiltration and, in 1991, sued Warner-Jenkinson for patent
infringement.
As trial approached, Hilton Davis conceded that there was no
literal infringement, and relied solely on the doctrine of
equivalents. Over Warner-Jenkinson's objection that the doctrine of
equivalents was an equitable doctrine to be applied by the court,
the issue of equivalence was included among those sent to the jury.
The jury found that the '746 patent was not invalid and that
Warner-Jenkinson infringed upon the patent under the doctrine of
equivalents. The jury also found, however, that Warner-Jenkinson
had not intentionally infringed, and therefore awarded only 20% of
the damages sought by Hilton Davis. The District Court denied
Warner-Jenkinson's post-trial motions, and entered a permanent
injunction prohibiting Warner-Jenkinson from practicing
ultrafiltration below 500 p. s. i. g. and below 9.01 pH. A
fractured en banc Court of Appeals for the Federal Circuit
affirmed.
62 F.3d
1512 (1995).
The majority below held that the doctrine of equivalents
continues to exist and that its touchstone is whether substantial
differences exist between the accused process and the patented
process.
Id., at 1521-1522. The court also held that the
question of equivalence is for the jury to decide and that the jury
in this case had substantial evidence from which it could conclude
that the Warner-Jenkinson process was not substantially different
from the ultrafiltration process disclosed in the '746 patent.
Id., at 1525.
There were three separate dissents, commanding a total of 5 of
12 judges. Four of the five dissenting judges viewed the doctrine
of equivalents as allowing an improper expan-
24
sion of claim scope, contrary to this Court's numerous holdings
that it is the claim that defines the invention and gives notice to
the public of the limits of the patent monopoly.
Id., at
1537-1538 (opinion of Plager, J.). The fifth dissenter, the late
Judge Nies, was able to reconcile the prohibition against enlarging
the scope of claims and the doctrine of equivalents by applying the
doctrine to each element of a claim, rather than to the accused
product or process "overall."
Id., at 1574. As she explained
it: "The 'scope' is not enlarged if courts do not go beyond the
substitution of equivalent elements."
Ibid. All of the
dissenters, however, would have found that a much narrowed doctrine
of equivalents may be applied in whole or in part by the court.
Id., at 1540-1542 (opinion of Plager, J.);
id., at
1579 (opinion of Nies, J.).
We granted certiorari, 516 U. S. 1145 (1996), and now reverse
and remand.
II
In
Graver Tank we considered the application of the
doctrine of equivalents to an accused chemical composition for use
in welding that differed from the patented welding material by the
substitution of one chemical element. 339 U. S., at 610. The
substituted element did not fall within the literal terms of the
patent claim, but the Court nonetheless found that the "question
which thus emerges is whether the substitution [of one element for
the other] ... is a change of such substance as to make the
doctrine of equivalents inapplicable; or conversely, whether under
the circumstances the change was so insubstantial that the trial
court's invocation of the doctrine of equivalents was justified."
Ibid. The Court also described some of the considerations
that go into applying the doctrine of equivalents:
"What constitutes equivalency must be determined against the
context of the patent, the prior art, and the particular
circumstances of the case. Equivalence, in the patent law, is not
the prisoner of a formula and is
25
not an absolute to be considered in a vacuum. It does not
require complete identity for every purpose and in every respect.
In determining equivalents, things equal to the same thing may not
be equal to each other and, by the same token, things for most
purposes different may sometimes be equivalents. Consideration must
be given to the purpose for which an ingredient is used in a
patent, the qualities it has when combined with the other
ingredients, and the function which it is intended to perform. An
important factor is 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." Id., at 609.
Considering those factors, the Court viewed the difference
between the chemical element claimed in the patent and the
substitute element to be "colorable only," and concluded that the
trial court's judgment of infringement under the doctrine of
equivalents was proper.
Id., at 612.
A
Petitioner's primary argument in this Court is that the doctrine
of equivalents, as set out in
Graver Tank in 1950, did not
survive the 1952 revision of the Patent Act, 35 U. s. C. § 100
et seq., because it is inconsistent with several aspects of
that Act. In particular, petitioner argues: (1) The doctrine of
equivalents is inconsistent with the statutory requirement that a
patentee specifically "claim" the invention covered by a patent, §
112; (2) the doctrine circumvents the patent reissue
process-designed to correct mistakes in drafting or the like-and
avoids the express limitations on that process, §§ 251-252; (3) the
doctrine is inconsistent with the primacy of the Patent and
Trademark Office (PTO) in setting the scope of a patent through the
patent prosecution process; and (4) the doctrine was implicitly
rejected as a general matter by Congress' specific and limited
inclusion of the doctrine
26
in one section regarding "means" claiming, § 112, , 6. All but
one of these arguments were made in
Graver Tank in the
context of the 1870 Patent Act, and failed to command a
majority.3
The 1952 Patent Act is not materially different from the 1870
Act with regard to claiming, reissue, and the role of the PTO.
Compare,
e. g., 35 U. S. C. § 112 ("The specification
shall conclude with one or more claims particularly pointing out
and distinctly claiming the subject matter which the applicant
regards as his invention") with the Consolidated Patent Act of
1870, ch. 230, § 26, 16 Stat. 198, 201 (the applicant "shall
particularly point out and distinctly claim the part, improvement,
or combination which he claims as his invention or discovery").
Such minor differences as exist between those provisions in the
1870 and the 1952 Acts have no bearing on the result reached in
Graver Tank, and thus provide no basis for our overruling
it. In the context of infringement, we have already held that
pre-1952 precedent survived the passage of the 1952 Act. See
Aro
Mfg. Co. v.
Convertible Top Replacement Co., 365 U. S. 336, 342 (1961)
(new section defining infringement "left intact the entire
3 Graver Tank was decided over a vigorous dissent.
In that dissent, Justice Black raised the first three of
petitioner's four arguments against the doctrine of equivalents.
See 339 U. S., at 613-614 (doctrine inconsistent with statutory
requirement to "distinctly claim" the invention);
id., at
614-615 (patent reissue process available to correct mistakes);
id., at 615, n. 3 (duty lies with the Patent Office to
examine claims and to conform them to the scope of the invention;
inventors may appeal Patent Office determinations if they disagree
with result).
Indeed, petitioner's first argument was not new even in 1950.
Nearly 100 years before
Graver Tank, this Court approved of
the doctrine of equivalents in
Winans v.
Denmead, 15
How. 330 (1854). The dissent in
Winans unsuccessfully argued
that the majority result was inconsistent with the requirement in
the 1836 Patent Act that the applicant "particularly 'specify and
point' out what he claims as his invention," and that the patent
protected nothing more.
Id., at 347 (opinion of Campbell,
J.).
27
body of case law on direct infringement"). We see no reason to
reach a different result here.4
Petitioner's fourth argument for an implied congressional
negation of the doctrine of equivalents turns on the reference to
"equivalents" in the "means" claiming provision of the 1952 Act.
Section 112, , 6, a provision not contained in the 1870 Act,
states:
"An element in a claim for a combination may be expressed as a
means or step for performing a specified function without the
recital of structure, material, or acts in support thereof, and
such claim shall be construed to cover the corresponding structure,
material, or acts described in the specification and equivalents
thereof" (Emphasis added.)
Thus, under this new provision, an applicant can describe an
element of his invention by the result accomplished or the function
served, rather than describing the item or element to be used
(e. g., "a means of connecting Part A to Part B," rather
than "a two-penny nail"). Congress enacted § 112, , 6, in response
to
Halliburton Oil Well Cementing Co. v.
Walker,
329 U. S. 1 (1946),
which rejected claims that "do not describe the invention but use
'conveniently functional language at the exact point of novelty.'"
Id., at 8 (citation
4 Petitioner argues that the evolution in patent practice from
"central" claiming (describing the core principles of the
invention) to "peripheral" claiming (describing the outer
boundaries of the invention) requires that we treat
Graver
Tank as an aberration and abandon the doctrine of equivalents.
Brief for Petitioner 43-45. We disagree. The suggested change in
claiming practice predates
Graver Tank, is not of statutory
origin, and seems merely to reflect narrower inventions in more
crowded arts. Also, judicial recognition of so-called "pioneer"
patents suggests that the abandonment of "central" claiming may be
overstated. That a claim describing a limited improvement in a
crowded field will have a limited range of permissible equivalents
does not negate the availability of the doctrine
vel
non.
28
omitted). See
In re Donaldson Co., 16
F.3d 1189, 1194 (CA Fed. 1994) (Congress enacted predecessor of
§ 112, , 6, in response to
Halliburton); In re Fuetterer,
319 F.2d
259, 264, n. 11 (CCPA 1963) (same); see also 2 D. Chisum,
Patents § 8.04[2], pp. 63-64 (1996) (discussing 1954 commentary of
then-Chief Patent Examiner P. J. Federico). Section 112, , 6, now
expressly allows so-called "means" claims, with the proviso that
application of the broad literal language of such claims must be
limited to only those means that are "equivalen[t]" to the actual
means shown in the patent specification. This is an application of
the doctrine of equivalents in a restrictive role, narrowing the
application of broad literal claim elements. We recognized this
type of role for the doctrine of equivalents in
Graver Tank
itself. 339 U. S., at 608-609. The added provision, however, is
silent on the doctrine of equivalents as applied where there is no
literal infringement.
Because § 112, , 6, was enacted as a targeted cure to a specific
problem, and because the reference in that provision to
"equivalents" appears to be no more than a prophylactic against
potential side effects of that cure, such limited congressional
action should not be overread for negative implications. Congress
in 1952 could easily have responded to
Graver Tank as it did
to the
Halliburton decision. But it did not. Absent
something more compelling than the dubious negative inference
offered by petitioner, the lengthy history of the doctrine of
equivalents strongly supports adherence to our refusal in
Graver
Tank to find that the Patent Act conflicts with that doctrine.
Congress can legislate the doctrine of equivalents out of existence
any time it chooses. The various policy arguments now made by both
sides are thus best addressed to Congress, not this Court.
B
We do, however, share the concern of the dissenters below that
the doctrine of equivalents, as it has come to be applied since
Graver Tank, has taken on a life of its own, unbounded
29
by the patent claims. There can be no denying that the doctrine
of equivalents, when applied broadly, conflicts with the
definitional and public-notice functions of the statutory claiming
requirement. Judge Nies identified one means of avoiding this
conflict:
"[A] distinction can be drawn that is not too esoteric between
substitution of an equivalent for a component in an
invention and enlarging the metes and bounds of the invention
beyond what is claimed.
"Where a claim to an invention is expressed as a combination of
elements, as here, 'equivalents' in the sobriquet 'Doctrine of
Equivalents' refers to the equivalency of an element or
part of the invention with one that is substituted in the
accused product or process.
"This view that the accused device or process must be more than
'equivalent' overall reconciles the Supreme Court's position
on infringement by equivalents with its concurrent statements that
'the courts have no right to enlarge a patent beyond the scope of
its claims as allowed by the Patent Office.' [Citations omitted.]
The 'scope' is not enlarged if courts do not go beyond the
substitution of equivalent elements." 62 F. 3d, at 15731574
(dissenting opinion) (emphasis in original).
We concur with this apt reconciliation of our two lines of
precedent. Each element contained in a patent claim is deemed
material to defining the scope of the patented invention, and thus
the doctrine of equivalents must be applied to individual elements
of the claim, not to the invention as a whole. It is important to
ensure that the application of the doctrine, even as to an
individual element, is not allowed such broad playas to effectively
eliminate that element in its entirety. So long as the doctrine of
equivalents does not encroach beyond the limits just described, or
beyond related
30
limits to be discussed
infra this page and 31-34, 39, n.
8, and 39-40, we are confident that the doctrine will not vitiate
the central functions of the patent claims themselves.
III
Understandably reluctant to assume this Court would overrule
Graver Tank, petitioner has offered alternative arguments in
favor of a more restricted doctrine of equivalents than it feels
was applied in this case. We address each in turn.
A
Petitioner first argues that
Graver Tank never purported
to supersede a well-established limit on nonliteral infringement,
known variously as "prosecution history estoppel" and "file wrapper
estoppel." See
Bayer Aktiengesellschaft v.
Duphar Int'Z
Research B. V:,
738 F.2d
1237, 1238 (CA Fed. 1984). According to petitioner, any
surrender of subject matter during patent prosecution, regardless
of the reason for such surrender, precludes recapturing any part of
that subject matter, even if it is equivalent to the matter
expressly claimed. Because, during patent prosecution, respondent
limited the pH element of its claim to pH levels between 6.0 and
9.0, petitioner would have those limits form bright lines beyond
which no equivalents may be claimed. Any inquiry into the reasons
for a surrender, petitioner claims, would undermine the public's
right to clear notice of the scope of the patent as embodied in the
patent file.
We can readily agree with petitioner that
Graver Tank did
not dispose of prosecution history estoppel as a legal limit ation
on the doctrine of equivalents. But petitioner reaches too far in
arguing that the reason for an amendment during patent prosecution
is irrelevant to any subsequent estoppel. In each of our cases
cited by petitioner and by the dissent below, prosecution history
estoppel was tied to amendments made to avoid the prior art, or
otherwise to address a specific concern-such as obviousness-that
arguably would have
31
rendered the claimed subject matter unpatentable. Thus, in
Exhibit Supply Co. v.
Ace Patents Corp., 315 U. S. 126 (1942),
Chief Justice Stone distinguished inclusion of a limiting phrase in
an original patent claim from the "very different" situation in
which "the applicant, in order to meet objections in the Patent
Office,
based on references to the prior art, adopted the
phrase as a substitute for the broader one" previously used.
Id., at 136 (emphasis added). Similarly, in
Keystone
Driller Co. v.
Northwest Engineering Corp., 294 U. S. 42 (1935),
estoppel was applied where the initial claims were "rejected on the
prior art,"
id., at 48, n. 6, and where the allegedly
infringing equivalent element was outside of the revised claims and
within the prior art that formed the basis for the rejection of the
earlier claims,
id., at 48.5
It is telling that in each case this Court probed the reasoning
behind the Patent Office's insistence upon a change in the claims.
In each instance, a change was demanded because the claim as
otherwise written was viewed as not describing a patentable
invention at all-typically because what it described was
encompassed within the prior art. But, as the United States informs
us, there are a variety of other reasons why the PTO may request a
change in claim language. Brief for United States as
Amicus
Curiae 22-23
5 See also
Smith v.
Magic City Kennel Club, Inc.,
282 U. S. 784,
788 (1931) (estoppel applied to amended claim where the original
"claim was rejected on the prior patent to" another);
Computing
Scale Co. of America v.
Automatic Scale Co., 204 U. S. 609, 618-620
(1907) (initial claims rejected based on lack of invention over
prior patents);
Hubbell v.
United States, 179 U. S. 77, 83 (1900)
(patentee estopped from excluding a claim element where element was
added to overcome objections based on lack of novelty over prior
patents);
Sutter v.
Robinson, 119 U. S. 530, 541 (1886)
(estoppel applied where, during patent prosecution, the applicant
"was expressly required to state that [the device's] structural
plan was old and not of his invention"); cf.
Graham v.
John Deere Co. of Kansas City, 383 U. S. 1, 33 (1966)
(noting, in a validity determination, that "claims that have been
narrowed in order to obtain the issuance of a patent by
distinguishing the prior art cannot be sustained to cover that
which was previously by limitation eliminated from the
patent").
32
(counsel for the PTO also appearing on the brief). And if the
PTO has been requesting changes in claim language without the
intent to limit equivalents or, indeed, with the expectation that
language it required would in many cases allow for a range of
equivalents, we should be extremely reluctant to upset the basic
assumptions of the PTO without substantial reason for doing so. Our
prior cases have consistently applied prosecution history estoppel
only where claims have been amended for a limited set of reasons,
and we see no substantial cause for requiring a more rigid rule
invoking an estoppel regardless of the reasons for a change.6
In this case, the patent examiner objected to the patent claim
due to a perceived overlap with the Booth patent, which revealed an
ultrafiltration process operating at a pH above 9.0. In response to
this objection, the phrase "at a pH from approximately 6.0 to 9.0"
was added to the claim. While it is undisputed that the upper limit
of 9.0 was added in order to distinguish the Booth patent, the
reason for adding the lower limit of 6.0 is unclear. The lower
limit certainly did not serve to distinguish the Booth patent,
which said nothing about pH levels below 6.0. Thus, while a lower
limit of 6.0, by its mere inclusion, became a material
element of the claim, that did not necessarily preclude the
application of the doctrine of equivalents as to that element. See
Hubbell v.
United States, 179 U. S. 77, 82 (1900) ("
'[A]ll [specified elements] must be regarded as material,'" though
it remains an open "'question whether an omitted part is supplied
by an equivalent device or instrumentality'" (citation
omitted)).
6 That petitioner's rule might provide a brighter line for
determining whether a patentee is estopped under certain
circumstances is not a sufficient reason for adopting such a rule.
This is especially true where, as here, the PTO may have relied
upon a flexible rule of estoppel when deciding whether to ask for a
change in the first place. To change so substantially the rules of
the game now could very well subvert the various balances the PTO
sought to strike when issuing the numerous patents which have not
yet expired and which would be affected by our decision.
33
Where the reason for the change was not related to avoiding the
prior art, the change may introduce a new element, but it does not
necessarily preclude infringement by equivalents of that
element.7
We are left with the problem, however, of what to do in a case
like the one at bar, where the record seems not to reveal the
reason for including the lower pH limit of 6.0. In our view,
holding that certain reasons for a claim amendment may avoid the
application of prosecution history estoppel is not tantamount to
holding that the
absence of a reason for an amendment may
similarly avoid such an estoppel. Mindful that claims do indeed
serve both a definitional and a notice function, we think the
better rule is to place the burden on the patent holder to
establish the reason for an amendment required during patent
prosecution. The court then would decide whether that reason is
sufficient to overcome prosecution history estoppel as a bar to
application of the doctrine of equivalents to the element added by
that amendment. Where no explanation is established, however, the
court should presume that the patent applicant had a substantial
reason related to patentability for including the limiting element
added by amendment. In those circumstances, prosecution history
estoppel would bar the application of the doctrine of equivalents
as to that element. The presumption we have described, one subject
to rebuttal if an appropriate reason for a required amendment is
established, gives proper deference to the role of claims in
defining an invention and providing public notice, and to the
primacy of
7We do not suggest that, where a change is made to overcome an
objection based on the prior art, a court is free to review the
correctness of that objection when deciding whether to apply
prosecution history estoppel. As petitioner rightly notes, such
concerns are properly addressed on direct appeal from the denial of
a patent, and will not be revisited in an infringement action.
Smith v.
Magic City Kennel Club, Inc., supra, at
789-790. What
is permissible for a court to explore is the
reason (right or wrong) for the objection and the manner in which
the amendment addressed and avoided the objection.
34
the PTO in ensuring that the claims allowed cover only subject
matter that is properly patentable in a proffered patent
application. Applied in this fashion, prosecution history estoppel
places reasonable limits on the doctrine of equivalents, and
further insulates the doctrine from any feared conflict with the
Patent Act.
Because respondent has not proffered in this Court a reason for
the addition of a lower pH limit, it is impossible to tell whether
the reason for that addition could properly avoid an estoppel.
Whether a reason in fact exists, but simply was not adequately
developed, we cannot say. On remand, the Federal Circuit can
consider whether reasons for that portion of the amendment were
offered or not and whether further opportunity to establish such
reasons would be proper.
B
Petitioner next argues that even if
Graver Tank remains
good law, the case held only that the absence of substantial
differences was a
necessary element for infringement under
the doctrine of equivalents, not that it was
sufficient for
such a result. Brief for Petitioner 32. Relying on
Graver
Tank's references to the problem of an "unscrupulous copyist"
and "piracy," 339 U. S., at 607, petitioner would require judicial
exploration of the equities of a case before allowing application
of the doctrine of equivalents. To be sure,
Graver Tank
refers to the prevention of copying and piracy when describing the
benefits of the doctrine of equivalents. That the doctrine produces
such benefits, however, does not mean that its application is
limited only to cases where those particular benefits are
obtained.
Elsewhere in
Graver Tank the doctrine is described in
more neutral terms. And the history of the doctrine as relied upon
by
Graver Tank reflects a basis for the doctrine not so
limited as petitioner would have it. In
Winans v.
Denmead, 15 How. 330, 343 (1854), we described the
doctrine
35
of equivalents as growing out of a legally implied term in each
patent claim that "the claim extends to the thing patented, however
its form or proportions may be varied." Under that view,
application of the doctrine of equivalents involves determining
whether a particular accused product or process infringes upon the
patent claim, where the claim takes the form-half express, half
implied-of "X and its equivalents."
Machine Co. v.
Murphy, 97 U. S. 120, 125 (1878),
on which
Graver Tank also relied, offers a similarly
intent-neutral view of the doctrine of equivalents:
"[T]he substantial equivalent of a thing, in the sense of the
patent law, is the same as the thing itself; so that if two devices
do the same work in substantially the same way, and accomplish
substantially the same result, they are the same, even though they
differ in name, form, or shape."
If the essential predicate of the doctrine of equivalents is the
notion of identity between a patented invention and its equivalent,
there is no basis for treating an infringing equivalent any
differently from a device that infringes the express terms of the
patent. Application of the doctrine of equivalents, therefore, is
akin to determining literal infringement, and neither requires
proof of intent.
Petitioner also points to
Graver Tank's seeming reliance
on the absence of independent experimentation by the alleged
infringer as supporting an equitable defense to the doctrine of
equivalents. The Federal Circuit explained this factor by
suggesting that an alleged infringer's behavior, be it copying,
designing around a patent, or independent experimentation,
indirectly reflects the substantiality of the differences between
the patented invention and the accused device or process. According
to the Federal Circuit, a person aiming to copy or aiming to avoid
a patent is imagined to be at
36
least marginally skilled at copying or avoidance, and thus
intentional copying raises an inference-rebuttable by proof of
independent development-of having only insubstantial differences,
and intentionally designing around a patent claim raises an
inference of substantial differences. This explanation leaves much
to be desired. At a minimum, one wonders however to distinguish
between the intentional copyist making minor changes to lower the
risk of legal action and the incremental innovator designing around
the claims, yet seeking to capture as much as is permissible of the
patented advance.
But another explanation is available that does not require a
divergence from generally objective principles of patent
infringement. In both instances in
Graver Tank where we
referred to independent research or experiments, we were discussing
the known interchangeability between the chemical compound claimed
in the patent and the compound substituted by the alleged
infringer. The need for independent experimentation thus could
reflect knowledge-or lack thereof-of interchangeability possessed
by one presumably skilled in the art. The known interchangeability
of substitutes for an element of a patent is one of the express
objective factors noted by
Graver Tank as bearing upon
whether the accused device is substantially the same as the
patented invention. Independent experimentation by the alleged
infringer would not always reflect upon the objective question
whether a person skilled in the art would have known of the
interchangeability between two elements, but in many cases it would
likely be probative of such knowledge.
Although
Graver Tank certainly leaves room for
petitioner's suggested inclusion of intent-based elements in the
doctrine of equivalents, we do not read it as requiring them. The
better view, and the one consistent with
Graver Tank's
predecessors and the objective approach to infringement, is that
intent plays no role in the application of the doctrine of
equivalents.
37
C
Finally, petitioner proposes 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. A milder version of this argument, which
found favor with the dissenters below, is that the doctrine should
be limited to equivalents that were known at the time the patent
was issued, and should not extend to after-arising equivalents.
As we have noted,
supra, at 36, with regard to the
objective nature of the doctrine, a skilled practitioner's
knowledge of the interchangeability between claimed and accused
elements is not relevant for its own sake, but rather for what it
tells the factfinder about the similarities or differences between
those elements. Much as the perspective of the hypothetical
"reasonable person" gives content to concepts such as "negligent"
behavior, the perspective of a skilled practitioner provides
content to, and limits on, the concept of "equivalence." Insofar as
the question under the doctrine of equivalents is whether an
accused element is equivalent to a claimed element, the proper time
for evaluating equivalency-and thus knowledge of interchangeability
between elements-is at the time of infringement, not at the time
the patent was issued. And rejecting the milder version of
petitioner's argument necessarily rejects the more severe
proposition that equivalents must not only be known, but must also
be actually disclosed in the patent in order for such equivalents
to infringe upon the patent.
IV
The various opinions below, respondents, and
amici devote
considerable attention to whether application of the doctrine of
equivalents is a task for the judge or for the jury. However,
despite petitioner's argument below that the doctrine should be
applied by the judge, in this Court petitioner makes only passing
reference to this issue. See Brief for
38
Petitioner 22, n. 15 ("If this Court were to hold in
Markman v.
Westview Instruments, Inc., No. 95-26
(argued Jan. 8, 1996), that judges rather than juries are to
construe patent claims, so as to provide a uniform definition of
the scope of the legally protected monopoly, it would seem at
crosspurposes to say that juries may nonetheless expand the claims
by resort to a broad notion of 'equivalents' "); Reply Brief for
Petitioner 20 (whether judge or jury should apply the doctrine of
equivalents depends on how the Court views the nature of the
inquiry under the doctrine of equivalents).
Petitioner's comments go more to the alleged inconsistency
between the doctrine of equivalents and the claiming requirement
than to the role of the jury in applying the doctrine as properly
understood. Because resolution of whether, or how much of, the
application of the doctrine of equivalents can be resolved by the
court is not necessary for us to answer the question presented, we
decline to take it up. The Federal Circuit held that it was for the
jury to decide whether the accused process was equivalent to the
claimed process. There was ample support in our prior cases for
that holding. See,
e. g., Machine Co. v.
Murphy, 97
U. S., at 125 ("[I]n determining the question of infringement, the
court or jury, as the case may be, ... are to look at the machines
or their several devices or elements in the light of what they do,
or what office or function they perform, and how they perform it,
and to find that one thing is substantially the same as another, if
it performs substantially the same function in substantially the
same way to obtain the same result");
Winans v.
Denmead, 15 How., at 344 ("[It] is a question for the jury"
whether the accused device was "the same in kind, and effected by
the employment of [the patentee's] mode of operation in
substance"). Nothing in our recent decision in
Markman v.
Westview Instruments, Inc., 517 U. S. 370 (1996),
necessitates a different result than that reached by the Federal
Circuit. Indeed,
Markman cites with considerable favor, when
discussing the role of judge
39
and jury, the seminal
Winans decision. 517 U. S., at
384385. Whether, if the issue were squarely presented to us, we
would reach a different conclusion than did the Federal Circuit is
not a question we need decide today.8
V
All that remains is to address the debate regarding the
linguistic framework under which "equivalence" is determined. Both
the parties and the Federal Circuit spend considerable time arguing
whether the so-called "triple identity" test-focusing on the
function served by a particular claim element, the
way that element serves that function, and the
result
thus obtained by that element-is a suitable method for determining
equivalence, or whether an "insubstantial differences" approach is
better. There seems to be substantial agreement that, while the
triple identity test may be suitable for analyzing mechanical
devices, it often
8With regard to the concern over unreviewability due to
black-box jury verdicts, we offer only guidance, not a specific
mandate. Where the evidence is such that no reasonable jury could
determine two elements to be equivalent, district courts are
obliged to grant partial or complete summary judgment. See Fed.
Rule Civ. Proc. 56;
Celotex Corp. v.
Catrett,
477 U. S. 317,
322-323 (1986). If there has been a reluctance to do so by some
courts due to unfamiliarity with the subject matter, we are
confident that the Federal Circuit can remedy the problem. Of
course, the various legal limitations on the application of the
doctrine of equivalents are to be determined by the court, either
on a pretrial motion for partial summary judgment or on a motion
for judgment as a matter of law at the close of the evidence and
after the jury verdict. Fed. Rule Civ. Proc. 56; Fed. Rule Civ.
Proc. 50. Thus, under the particular facts of a case, if
prosecution history estoppel would apply or if a theory of
equivalence would entirely vitiate a particular claim element,
partial or complete judgment should be rendered by the court, as
there would be no further
material issue for the jury to
resolve. Finally, in cases that reach the jury, a special verdict
and/or interrogatories on each claim element could be very useful
in facilitating review, uniformity, and possibly postverdict
judgments as a matter of law. See Fed. Rules Civ. Proc. 49 and 50.
We leave it to the Federal Circuit how best to implement procedural
improvements to promote certainty, consistency, and reviewability
to this area of the law.
40
provides a poor framework for analyzing other products or
processes. On the other hand, the insubstantial differences test
offers little additional guidance as to what might render any given
difference "insubstantial."
In our view, the particular linguistic framework used 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. A focus on
individual elements and a special vigilance against allowing the
concept of equivalence to eliminate completely any such elements
should reduce considerably the imprecision of whatever language is
used. An analysis of the role played by each element in the context
of the specific patent claim will thus inform the inquiry as to
whether a substitute element matches the function, way, and result
of the claimed element, or whether the substitute element plays a
role substantially different from the claimed element. With these
limiting principles as a backdrop, we see no purpose in going
further and micromanaging the Federal Circuit's particular word
choice for analyzing equivalence. We expect that the Federal
Circuit will refine the formulation of the test for equivalence in
the orderly course of case-by-case determinations, and we leave
such refinement to that court's sound judgment in this area of its
special expertise.
VI
Today we adhere to the doctrine of equivalents. The
determination of equivalence should be applied as an objective
inquiry on an element-by-element basis. Prosecution history
estoppel continues to be available as a defense to infringement,
but if the patent holder demonstrates that an amendment required
during prosecution had a purpose unrelated to patentability, a
court must consider that purpose in
41
order to decide whether an estoppel is precluded. Where the
patent holder is unable to establish such a purpose, a court should
presume that the purpose behind the required amendment is such that
prosecution history estoppel would apply. Because the Court of
Appeals for the Federal Circuit did not consider all of the
requirements as described by us today, particularly as related to
prosecution history estoppel and the preservation of some meaning
for each element in a claim, we reverse its judgment and remand the
case for further proceedings consistent with this opinion.
It is so ordered.
JUSTICE GINSBURG, with whom JUSTICE KENNEDY joins,
concurring.
I join the opinion of the Court and write separately to add a
cautionary note on the rebuttable presumption the Court announces
regarding prosecution history estoppel. I address in particular the
application of the presumption in this case and others in which
patent prosecution has already been completed. The new presumption,
if applied woodenly, might in some instances unfairly discount the
expectations of a patentee who had no notice at the time of patent
prosecution that such a presumption would apply. Such a patentee
would have had little incentive to insist that the reasons for all
modifications be memorialized in the file wrapper as they were
made. Years after the fact, the patentee may find it difficult to
establish an evidentiary basis that would overcome the new
presumption. The Court's opinion is sensitive to this problem,
noting that "the PTO may have relied upon a flexible rule of
estoppel when deciding whether to ask for a change" during patent
prosecution.
Ante, at 32, n. 6.
Because respondent has not presented to this Court any
explanation for the addition of the lower pH limit, I concur in the
decision to remand the matter to the Federal Circuit.
42
On remand, that court can determine-bearing in mind the prior
absence of clear rules of the game-whether suitable reasons for
including the lower pH limit were earlier offered or, if not,
whether they can now be established.
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