Patent Law: The Festo Case and the Doctrine of Equivalents

Report for Congress
Patent Law: The Festo Case
and the Doctrine of Equivalents
Updated July 25, 2002
Margaret Mikyung Lee
Legislative Attorney
American Law Division


Congressional Research Service ˜ The Library of Congress

Patent Law: The Festo Case and the Doctrine of
Equivalents
Summary
On May 28, 2002, the U.S. Supreme Court handed down its unanimous decision
in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., 535 U.S. ___, 122
S. Ct. 1831, 152 L. Ed. 2d 944 [hereinafter Festo], reversing the most controversial
of the holdings in the case by the U.S. Court of Appeals for the Federal Circuit
(CAFC), vacating the decision, and remanding the case for further proceedings. The
CAFC decision had been criticized as upsetting well-settled expectations and
understandings concerning the operation of certain legal principles, namely, the
doctrine of equivalents and prosecution history estoppel. The doctrine of equivalents
provides that a product or process that does not literally infringe a patent can still be
found to be infringing if the differences between the allegedly infringing product or
process and the patented invention are minimal and insubstantial, that is, if the
allegedly infringing product or process is substantially equivalent to the patented
invention. The doctrine of equivalents is limited by prosecution history estoppel.
Prosecution history estoppel provides that, as a patent applicant surrenders subject
matter during prosecution to avoid rejection, i.e., amends claims to narrow them for
reasons related to patentability, the patentee also surrenders that subject matter for
purposes of any infringement suit based on the doctrine of equivalents. For example,
an applicant applies to patent a plastic-top table with metal legs. The examiner
rejects the claim for metal legs because prior art includes a plastic-top table with rigid
metal legs, so the applicant narrows the claim to distinguish it from prior art by
amending it to cover a plastic-top table with collapsible metal legs folding into two
parts; the patent is granted. The patentee cannot now claim that a plastic-top table
with rigid metal legs is equivalent and should be found infringing, because the
patentee surrendered rigid metal legs in the narrowing amendment. In the past the
CAFC had applied a “flexible bar” rule which meant that, out of a range of possible
equivalents, e.g., a plastic-topped metal-legged table that folds differently from the
patented table, prosecution history estoppel did not necessarily bar a finding of
infringement under the doctrine of equivalents for the entire range. In Festo, the
CAFC established a new “complete bar” rule which meant prosecution history
estoppel would completely bar the application of the doctrine of equivalents.
The Supreme Court reversed this holding, reinstating and affirming the “flexible
bar” rule as the appropriate rule and the one more consistent with the spirit of the
doctrine of equivalents. At the same time, the Court affirmed the holding of the
CAFC that prosecution history estoppel applies to an amendment which narrowed
claims in order to satisfy any patent requirement, rejecting the petitioner’s argument
that such estoppel only applies to an amendment which narrowed claims to avoid
prior art. The Court remanded the case for further proceedings to decide whether the
amendments made by the Festo Corporation surrendered the particular equivalents
at issue in the case under the “flexible bar” rule. It noted that the concerns of those
who desired a clearer, “bright line” rule with regard to estoppel and equivalents
would be best directed to Congress which could alter the doctrine legislatively. In
the wake of its Festo decision, on June 3, 2002, the Supreme Court granted certiorari
in nine patent cases, then vacated prior rulings in those cases and remanded them for
further proceedings taking into consideration the rules announced in Festo.



Contents
Background ......................................................1
The Festo Case in the Lower Courts...................................4
Patents at Issue and Early Procedural History........................4
En Banc Decision in the Federal Circuit............................5
Opinion of the Court.......................................5
Concurrences and Dissents..................................7
The U.S. Supreme Court Decision.....................................8
Petitioner’s Arguments.........................................8
Respondent’s Arguments........................................9
Government’s Arguments......................................10
Supreme Court Opinion........................................10
Festo-Related Cases...............................................12
Pioneer Magnetics, Inc. v. Micro Linear Corp., ___ U.S. ___, 122 S. Ct.
2322, 153 L. Ed. 2d 151 (2002)..........................12
Insituform Technologies v. CAT Contracting, et al., ___ U.S. ___, 122 S.
Ct. 2322, 153 L. Ed. 2d 151 (2002).......................12
Senior Technologies, Inc. v. R. F. Technologies, Inc., ___ U.S. ___, 122
S. Ct. 2323, 153 L. Ed. 2d 151 (2002).....................12
Creo Products Inc. v. Dainippon Screen Mfg. Co., Ltd., et al., ___ U.S.
___, 122 S. Ct. 2323, 153 L. Ed. 2d 151 (2002).............13
Semitool, Inc. v. Novellus Systems, Inc., ___ U.S. ___, 122 S. Ct. 2323,
153 L. Ed. 2d 152 (2002)...............................13
Lockheed Martin Corp. v. Space Systems/Loral, Inc., ___ U.S. ___, 122
S. Ct. 2349, 153 L. Ed. 2d 152 (2002).....................13
AccuScan, Inc. v. Xerox Corp., ___ U.S. ___, 122 S. Ct. 2323, 153 L. Ed.
2d 152 (2002)........................................14
PTI Technologies, Inc. v. Pall Corp. Technologies, Inc., ___ U.S. ___, 122
S. Ct. 2324, 153 L. Ed. 2d 152 (2002).....................14
Mycogen Plant Science, et al. v. Monsanto Company, ___ U.S. ___, 122
S. Ct. 2324, 153 L. Ed. 2d 153 (2002).....................15
Other issues.............................................15



Patent Law: The Festo Case and the
Doctrine of Equivalents
On May 28, 2002, the U.S. Supreme Court handed down its unanimous decision
in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., 535 U.S. ___, 122
S. Ct. 1831, 152 L. Ed. 2d 944 [hereinafter Festo], reversing the most controversial
aspect of the holdings in the decision of the U.S. Court of Appeals for the Federal
Circuit (CAFC), vacating the decision, and remanding the case for further
proceedings. Last June, the Court had granted certiorari to consider a highly
controversial en banc opinion issued by the CAFC in the Festo case. This CAFC
opinion had been criticized as upsetting well-settled expectations and understandings
concerning the operation of certain patent law principles, namely, the doctrine of
equivalents and prosecution history estoppel, in favor of establishing a supposedly
clearer rule that would yield greater certainty about infringement. The Court held in
favor of restoring the flexible approach, noting that the policy arguments of those
who desired a clearer, “bright line” rule with regard to the doctrine of equivalents and
prosecution history estoppel would be best addressed to Congress which could alter
the doctrine legislatively.
Background
The patent application process is commonly referred to as a patent prosecution.
Generally, this is a non-adversarial process wherein the patent applicant submits the
application, consisting of specifications and claims delineating and describing the
invention, and engages in a dialogue with the patent examiner to further clarify and
distinguish the invention from the prior art, which consists of existing inventions.
Consequently, it is common for a patent applicant to amend the application to satisfy
objections and questions raised by the examiner. The applicant must provide in the
specifications a disclosure of the invention which is in “such full, clear, concise, and
exact terms as to enable any person skilled in the art . . . to make and use the same,
and shall set forth the best mode contemplated by the inventor of carrying out his
invention” (35 U.S.C. § 112). In the claims, the applicant must describe the
invention in a manner which distinguishes it as new and non-obvious compared with
the prior art, and must also describe the utility of the invention.1
Patent infringement occurs when a person uses, manufactures, sells, or imports
a product or process covered by an unexpired patent without authorization by the
patent holder. The patent holder typically will sue the alleged infringer seeking to


1The requirement of novelty is found at 35 U.S.C. §§ 101 and 102; the requirement of non-
obviousness is found at 35 U.S.C. § 103; and the requirement of utility or usefulness is
found at 35 U.S.C. § 101.

prevent further unauthorized activities and monetary damages. Once the patent is
established as valid, the court will analyze and compare literal language describing
the elements of the claims in the patent with the elements of the defendant’s product
or process to determine whether the patent claims completely cover every element
of the allegedly infringing product or process. If they do literally cover or “read on”
the product or device, then there is literal infringement by the defendant.
The Festo case concerns the application and interplay of two long-standing
principles of patent law: the doctrine of equivalents and prosecution history estoppel
(also known as file wrapper estoppel). The doctrine of equivalents provides that a
product or process that does not literally infringe a patent can still be found to be
infringing if the differences between the allegedly infringing product or process and
the patented invention are minimal and insubstantial, that is, if the allegedly
infringing product or process is substantially equivalent to the patented invention.
There is equivalents infringement if the elements of an infringing product or process
perform substantially the same function in substantially the same way to obtain the
same result as the elements of the patent claims. This doctrine evolved in the federal
courts around the mid-nineteenth century and is generally acknowledged to have been
first expressed and applied in a U.S. Supreme Court case in Winans v. Denmead, 15
How. 330, 14 L. Ed. 717 (1853). The doctrine seeks to balance the right of a patent
holder to a just and fair scope of protection with the right of the public and potential
competitors to know the scope of the patent protection granted to the patent holder.
Potential competitors must know with fair certainty the limits of the patent grant in
order to be able to innovate and “design around” the patent to avoid infringement; the
patent policy seeks to encourage further genuine innovation in a given industry. At
the same time, patent holders merit protection from competitors who attempt to
design around a patent with minor changes to elements of an invention covered by
a patent.
The doctrine of equivalents is limited by prosecution history estoppel.
Prosecution history estoppel provides that if a patent applicant surrenders subject
matter during prosecution to avoid rejection, i.e., amends claims to narrow them for
reasons of subject matter patentability, the patentee cannot later claim that this
surrendered subject matter is equivalent to surviving claims in the patent. For
example, an applicant applies to patent a plastic-top table with metal legs. The
examiner rejects the claim for metal legs because prior art includes a plastic-top table
with rigid metal legs. The applicant then narrows the claim to distinguish it from
prior art by amending it to cover a plastic-top table with collapsible metal legs
folding into two parts and the patent is granted. The patentee cannot now claim that
a plastic-top table with rigid metal legs is equivalent and should be found infringing,
because the patentee surrendered rigid metal legs in the narrowing amendment. The
patent applicant could surrender subject matter by amending a claim voluntarily or
at the request of the patent examiner. Additionally, the applicant could surrender
subject matter by making an argument on the record to answer the concerns of the
examiner without actually amending the claims. Before Festo, the standard for
applying both amendment-based and argument-based prosecution history estoppel
was whether a person reasonably skilled in the art would reasonably believe that the
patentee had surrendered subject matter during prosecution. This balanced the public
notice function of the prosecution history with the fair, adequate and just scope of
patent protection.



In Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997), the
U.S. Supreme Court explicitly affirmed the continued vitality of the doctrine of
equivalents, but established the “all elements” rule, clarifying that the allegedly
infringing product or process must be more than equivalent overall to the patented
invention, rather, the doctrine must be applied on an element-by-element basis.
Equivalence refers to the equivalence of a claimed element of a patented invention
with an element substituted in the allegedly infringing product or process.
Otherwise, an overall equivalence could expand a patent beyond its claims in a
manner which effectively eliminates a particular claimed element. In the example
of the plastic table with collapsible metal legs folding into two parts, assuming
estoppel did not apply, a court could not just look at an item that allegedly infringes
on the patent for that table, for example, a wood-top table with rigid metal legs, and
find that overall the wood-top table is equivalent to the plastic table. The court
would have to look at each element, the wood top and the rigid metal legs, and decide
whether the wood top was equivalent to the plastic top, the rigid metal legs
equivalent to the collapsible metal legs in two parts. Otherwise, a court might
eventually find that all tables are equivalent to each other since they perform the
same function in the same way, which would completely eliminate the significance
of any distinct element.
The Court further found that prosecution history estoppel was a valid defense
against infringement, but that if a patentee could demonstrate that an amendment was
made for a reason unrelated to patentability, a court must consider that reason to
determine whether estoppel is precluded. Where the reason for an amendment cannot
be determined from the prosecution record, a rebuttable presumption arises that the
reason is related to patentability and therefore that estoppel would apply. The burden
of proof is on the patentee to rebut the presumption and establish a reason unrelated
to patentability. In Warner-Jenkinson, Hilton Davis Chemical Company had applied
for a patent on an ultrafiltration purification process for dyes. During prosecution
the original claims were rejected because prior art existed for a process operating at
pH levels above 9.0. To distinguish the invention from prior art, Hilton Davis
amended the application to claim a process which operated at a pH range of 6.0 to
9.0. Then Warner-Jenkinson Company developed a process which operated at a pH
level of 5.0. Hilton Davis sued Warner-Jenkinson for infringement on the theory that
the process operating at a pH of 5.0 was equivalent to the process operating at a pH
of 6.0 to 9.0. Because the record did not reveal the reason why Hilton Davis
Chemical Company had added the lower pH 6.0 limit to the pH range, the Court
remanded the case for further proceedings to determine whether there was a reason
which might avoid estoppel. Per further discussion below, the Festo case had
previously been granted certiorari, vacated and remanded by the Supreme Court for
further consideration in light of Warner-Jenkinson.
With regard to the issue of the extent to which prosecution history estoppel
restricts the doctrine of equivalents, one should note the existence of two alternative
solutions, exemplified by two cases. One line of cases, leading back to Hughes
Aircraft Co. v. United States, 717 F.2d 1351 (Fed. Cir. 1983), applies the “flexible
bar” rule, under which there is a range of equivalents which may be available for a
claim element, not all of which are necessarily barred by prosecution history
estoppel. In the example of the plastic-topped table with the collapsible metal legs
folding into two parts, literal infringement would require an identical table and



claims of equivalence with regard to plastic-topped tables with rigid metal legs are
estopped. However, plastic-topped tables with collapsible legs folding into three
parts, while not literally infringing because each leg is in three parts, not two, could
lie within the range of equivalents because they perform substantially the same
function (folding up to be easily stored) in substantially the same way (collapsible
metal legs) to achieve the same object (an table that can be stored in a small space).
The Hughes case was the first case concerning this issue which the CAFC decided
after it was established in 1982. The other line of cases, leading back to Kinzenbaw
v. Deere & Co., 741 F.2d 383 (Fed. Cir. 1984), cert. denied, 470 U.S. 1004 (1984),
applies the “complete bar” rule, which provides that there is no range of equivalents;
the application of the doctrine of equivalents is completely barred. Although this rule
provides a “bright line” rule, it can have harsh consequences for a patentee. In the
example of the plastic-topped table with collapsible metal legs in two parts, not only
would claims of equivalence for rigid metal legs be estopped, but also any other
possible range of equivalents, such as the collapsible legs in three parts. The Hughes
“flexible bar” rule has been followed most often over the last twenty years.
The Festo Case in the Lower Courts
Patents at Issue and Early Procedural History
Festo Corporation had two patents – the “Stoll” patent and the “Carroll” patent
– concerning components of a conveyer belt system. The Stoll patent covered a
device consisting of a cylinder; a piston which moved inside the cylinder and
included magnets, two sealing rings, and two guide rings; and a sleeve which moved
outside the cylinder and included magnets and was made of a magnetizable material,
so that the movement of the piston inside the cylinder caused a corresponding
movement of the sleeve outside the cylinder. The patent examiner had originally
rejected all of the original claims, citing failure to satisfy the specification and claims
requirements under 35 U.S.C. § 112 and also citing three patents as pertinent
references. Stoll amended some claims and cancelled others in the application and
also cited two patents, including arguments with the amendments that the revised
claims were distinguishable from the cited patents. The amended language included
the description of the sleeve as made of magnetizable material.
The Carroll patent covered a device also consisting of a piston, cylinder and
sleeve arrangement. Carroll had requested reexamination of the patent to account for
a prior German patent that was not of record in the original prosecution history and
which called into question the patentability of the Carroll device. The claims were
amended to cite a pair of sealing rings on the piston engaging the cylinder to effect
a fluid-tight seal, and multiple magnets and cushioning parts on the piston. The
sleeve outside the cylinder of the Carroll device also included multiple magnets
which magnetically coupled the sleeve to the piston so that they moved together. The
sleeve also had a gripping device mounted on it to move objects along a conveyor
belt.
Festo sued Shoketsu Kinzoku Kogyo Kabushiki Company, also known as SMC
Corporation, for infringement of the two patents. The district court granted Festo



summary judgment of infringement of the Carroll patent. A jury concluded that both
patents were valid and found that a claim of the Stoll patent was infringed under the
doctrine of equivalents. The jury found that the non-magnetizable sleeve and single
sealing ring of SMC Corporation’s device performed substantially the same function
in substantially the same way as the magnetizable sleeve and two sealing rings of the
Stoll patented device. On appeal to the CAFC, the panel affirmed the judgment of
infringement under the doctrine of equivalents of the Stoll and Carroll patents.2 SMC
petitioned the Supreme Court for a writ of certiorari, which the Court granted. In the
meantime, the Court had decided Warner-Jenkinson and thus vacated the decision
of the CAFC in the Festo case and remanded it for consideration in light of Warner-
Jenkinson. A panel of the CAFC affirmed most of the earlier judgment again,
remanding it in part because the prior record was insufficient for the CAFC to make
a determination regarding prosecution history estoppel for the Stoll patent.3 SMC
Corporation petitioned for rehearing en banc, which the CAFC granted. The CAFC
sitting en banc reversed, holding that prosecution history estoppel completely barred
the application of the doctrine of equivalents.4
En Banc Decision in the Federal Circuit
Opinion of the Court.
The CAFC asked the parties to brief the following five questions and, by an 8-4
majority, answered them accordingly:
1.For the purposes of determining whether an amendment to a claim creates
prosecution history estoppel, is “a substantial reason related to patentability”
limited to those amendments made to overcome prior art under 35 U.S.C. §§
102 and 103 or does “patentability” mean any reason affecting the issuance of
a patent?
No, “a substantial reason related to patentability” is not limited to amendments
made to overcome prior art, but includes other reasons related to the statutory
requirements for a patent. Thus, any amendment narrowing the scope of a claim
element for any reason related to such requirements will give rise to estoppel
with respect to that claim element. The CAFC does not find this decision to be
inconsistent with Warner-Jenkinson, which focused on amendments to avoid
prior art but did not limit estoppel to such amendments. The rationale
underlying prosecution history estoppel, to prevent the patentee from
recapturing subject matter previously surrendered during prosecution, is valid
for amendments made for patentability reasons other than avoiding prior art. In
the instant case, the court found that the narrowing amendments made to the
Stoll patent to satisfy the requirements of 35 U.S.C. § 112 were amendments
made for a “a substantial reason related to patentability.” The court found that


272 F.3d 857 (Fed. Cir. 1995).
3172 F.3d 1361 (Fed. Cir. 1999).
4234 F.3d 558 (Fed. Cir. 2000).

the amendments made during the reexamination of the Carroll patent were
made, at least partly, to avoid the prior art of the German patent.
2.Under Warner-Jenkinson, should a voluntary claim amendment – one not
required by the examiner or made in response to a rejection by an examiner for
a stated reason – create prosecution history estoppel?
Yes. Voluntary claim amendments should be treated the same as other
amendments. There is no reason why estoppel should arise if a patent examiner
rejects a claim as unpatentable, but should not arise if the applicant voluntarily
amends a claim because he believes it to be unpatentable. Furthermore, this
holding is consistent with the doctrine of argument-based estoppel, under which
arguments made voluntarily during prosecution may give rise to estoppel if the
evidence a surrender of subject matter.

3.If a claim amendment creates prosecution history estoppel, under Warner-


Jenkinson what range of equivalents, if any, is available under the doctrine of
equivalents for the claim element so amended?
No range of equivalents is available for a claim amendment which creates
prosecution history estoppel. The application of the doctrine of equivalents is
completely barred. The court found that this issue of the range of equivalents
available under estoppel had never been before the Supreme Court and had
never been decided by it, contrary to the dissent of Judge Michel. It further
noted the Hughes case and the Kinzenbaw case, with their competing rules
regarding a flexible bar and complete bar, respectively. The court observed that
after twenty years of experience with the range-of-equivalents issue, it rejected
the “flexible bar” approach as resulting in too much uncertainty about the scope
of patent protection to fulfill adequately the public notice function of patent
claims. The “flexible bar” approach was “unworkable.” Under the certainty of
the “complete bar” approach, competitors of a patentee will be more inclined
to develop innovative elements of a product or process which otherwise might
lie within the uncertain range of equivalent products or processes around the
literal terms of a narrowed claim, free from the fear of infringement litigation.
4.When no explanation for a claim amendment is established, thus invoking the
presumption of prosecution history estoppel under Warner-Jenkinson, what
range of equivalents, if any, is available under the doctrine of equivalents for the
claim element so amended?
No range of equivalents is available for unexplained claim amendments. Under
Warner-Jenkinson, an unexplained amendment gives rise to a presumption that
the reason was related to patentability and thus prosecution history estoppel
applies against the doctrine of equivalents. Accordingly, it results in a complete
bar, just as for narrowing amendments known to be made for substantial reasons
related to patentability.
5.Would a judgment of infringement in this case violate the “all elements” rule
of Warner-Jenkinson, that is, the requirement that the application of the doctrine



of equivalents is not allowed such broad play as to eliminate an element in its
entirety?
This issue went unanswered; since the court found that prosecution history
estoppel applied completely to bar the doctrine of equivalents, it did not reach
this issue.
Concurrences and Dissents.
There were two concurring opinions. Judge Plager considered the CAFC
decision to be a “second-best solution to an unsatisfactory situation,” suggesting that
the best solution would be for the court to hold that the doctrine of equivalents is
firmly rooted in equity principles and to allow the courts to develop a set of known
factors to determine when the doctrine of equivalents would apply, thus allowing for
flexibility within a predictable analytical framework. Judge Lourie responded to the
proponents of the “flexible bar” rule, noting that it was not working, led to
uncertainty, encouraged clever lawyers to argue infringement outside the scope of
claims, and discouraged innovation. Although occasional injustices may result in
allowing some copiers to avoid infringement, overall, the new “complete bar” rule
would encourage innovation, lessen uncertainty and reduce litigation.
There were four opinions concurring in part and dissenting in part. Basically,
the dissenters took issue with the court’s resolution of issue no. 3, establishing a
complete bar, “bright line” rule governing the application of prosecution history
estoppel to the doctrine of equivalents. Judge Michel, joined by Judge Rader,
believed that the “complete bar” rule was inconsistent with Warner-Jenkinson and
other Supreme Court decisions; that the court’s holding provided a guide to
infringers, allowing them avoid infringement by making trivial modifications to
claimed elements which had patentability-related amendments; and that the
“complete bar” rule deprives most patentees of recourse to the doctrine of equivalents
because most patent claims were amended during the prosecution. Judge Rader
opined in his dissent that the new rule would completely eliminate patent protection
for amended claims with respect to after-arising technology, technology which comes
into existence after a patent is issued and is equivalent to the claimed invention. This
would be illogical, according to Judge Rader, because prosecution history estoppel
is intended to prevent a patentee from recapturing subject matter surrendered during
prosecution, but by definition, a patentee could not have surrendered after-arising
technology. Judge Linn foresaw an increase in the cost and complexity of patent
prosecutions to the detriment of individual inventors and start-up or smaller
businesses which do not have the resources to pursue lengthy, expensive
prosecutions. Furthermore, there would be an increased, undue emphasis on skill in
claims drafting. Like Judge Michel, Judge Linn believes that the new rule allows
unscrupulous copyists a free ride by providing a guide on how to avoid infringement.
Finally, Judge Newman also objected to the “complete bar” rule as a departure from
the holdings of Warner-Jenkinson and as a rejection of long-standing Supreme Court
and Federal Circuit precedent without adequate consideration and debate about the
impact of the new rule.



The U.S. Supreme Court Decision
Festo Corporation petitioned the Supreme Court for a writ of certiorari, which
was granted on June 18, 2001, at 121 S. Ct. 2519, 150 L. Ed. 2d 692 (2001) (Docket
No. 00-1543). In its petition for a writ of certiorari, Festo argued that the decision
of the CAFC disables the congressional scheme balancing the promotion of creativity
with certainty regarding the scope of the patent, noting that Congress could have
enacted laws expanding prosecution history estoppel and eliminating the doctrine of
equivalents if it had wanted to, but that it has not done so. The Court certified two
questions:
!Whether every claim-narrowing amendment designed to comply with any
provision of the Patent Act – including those provisions not related to prior art
– automatically creates prosecution history estoppel regardless of the reason
for the amendment; and
!Whether the finding of prosecution history estoppel completely bars the
application of the doctrine of equivalents.
Petitioner’s Arguments
In its brief on the certified issues, Festo argued that narrowing amendments
triggering prosecution history estoppel are limited to those made to avoid prior art or
to satisfy “substantive” statutory provisions concerning patentability, and do not
include amendments to satisfy requirements concerning the “form” of the
applications. With regard to the complete bar, Festo argued that the Court should
adhere to its traditional understanding of the reach of prosecution history estoppel,
that such estoppel does not completely bar every possible range of equivalents for an
amended claim element; and that the new rule would complicate patent prosecution
and litigation and would injure the patent system. Festo argued that the CAFC
decision departed from past precedent when it held that every narrowing amendment
to satisfy patent requirements gives rise to estoppel and then established its
“complete bar” rule. The petitioner alleged that the complete bar on equivalents cast
doubt on many currently existing, unexpired patents that were amended during
prosecution when narrowing amendments did not incur such a stringent penalty.
Festo and other critics of the “complete bar” rule alleged that a range of
undesirable consequences would arise from it,5 including:
!the drafting of narrower claims, with increased resort to litigation of doctrine
of equivalents issues in infringement suits as a means of avoiding narrowing
amendments which might give rise to prosecution history estoppel;


5Brief for Petitioner on writ of certiorari at 39-45 and Brief of Amicus Curiae American
Intellectual Property Law Association in support of petitioner at 13-19, Festo Corp. v.
Shoketsu Kinzoku Kogyo Kabushiki Co., (No. 00-1543); James Toupin & John Whealan,
Effects of Festo Decision on USPTO Operations (Feb. 28, 2001), at
http://www.uspto.gov/web/offices/com/advisory/ acrobat/ppacpres2-01.pdf.

!more arguments to overcome prior art rather than amendments, since the
“complete bar” rule apparently only applies to amendment-based estoppel, not
argument-based estoppel;
!more complex and expensive patent prosecutions disadvantaging smaller
companies and individuals;
!more refusals to amend to satisfy claim rejections and thus more frequent
appeals of claim rejections, which would burden the patent system, extend the
time before patent issuance and thus reduce the term of patent protection;
!harm to U.S. efforts with respect to international harmonization of patent
regimes;
!unfair retroactive application of the complete bar to the approximately 1.2
million extant patents that were issued prior to the Festo decision of the
CAFC, which would disturb well-settled expectations concerning the
operation of prosecution history estoppel to restrict application of the doctrine
of equivalents, possibly even implicating the Takings Clause of the Fifth
Amendment of the U.S. Constitution, according to at least one commentator;
!more reexamination requests by third-parties seeking to force amendments
giving rise to a complete bar to doctrine of equivalents under prosecution
history estoppel.
!filing of narrower claims, then trying to broaden them later (only narrowing
claims trigger prosecution history estoppel)
!more provisional applications being filed, with more precisely drafted
applications being filed later; and
!more extensive prior art searches and better disclosure (which may prove
beneficial in building the body of prior art for business methods patents).
Respondent’s Arguments
The respondent argued that the CAFC holding should be affirmed because the
narrowing amendments made by Festo were made to avoid prior art or were
unexplained and therefore are presumed under the Warner-Jenkinson rule to be
related to patentability. Reasons related to patentability were not limited to
avoidance of prior art, especially since a patent applicant could manipulate the
prosecution record by trying to characterize an amendment as merely clarifying an
ambiguity rather than narrowing the scope to avoid prior art. With regard to the
complete bar, the respondent argued that the CAFC adopted a rule supported in
Supreme Court precedent that any subject matter outside claim language after
amendment was automatically considered abandoned. The flexible bar was rightly
rejected as uncertain, unworkable and a deterrent to innovation and competition.
Finally, the respondent denies that any claim of reasonable reliance, that is, of
disruption of settled expectations regarding the doctrine of equivalents and
prosecution history estoppel, can defeat the CAFC adoption of a complete bar, noting



the alleged Supreme Court precedent for a complete bar and the realities of patent
practice.
Government’s Arguments
The Federal Government filed an amicus curiae brief and was granted
permission to participate in oral arguments. In its brief, the Government agreed that
the CAFC correctly held that prosecution history estoppel applies to claims amended
to comply with the Patent Act and not just to claims amended to avoid prior art;
however, it disagreed with the “complete bar” rule adopted by the CAFC. The
Government argued that a narrowing amendment to comply with any requirement of
the Patent Act gives rise to prosecution history estoppel with respect to the amended
portion of the claim and presumptively precludes application of the doctrine of
equivalents for the amended portion of the claim. This presumption can be rebutted
where the patentee shows a concrete basis, based on the prosecution history and
relevant to the specific context of the infringement suit, for a non-literal extension
of a claim element that was narrowed to secure a patent. The Government noted two
scenarios where the presumption might be rebutted: (1) the alleged equivalent is a
development of after-arising technology unforeseeable by persons of ordinary skill
in the art (field of the invention) at the time of the amendment6 and (2) the subject
matter of the claim is such that it would have been impossible for the patent applicant
to draft an amendment that literally encompassed the allegedly equivalent claim
element while disclaiming the surrendered subject matter.
Supreme Court Opinion
Justice Kennedy delivered the unanimous opinion of the Court on May 28,
2002, holding that any narrowing amendment made to satisfy any requirement of the
Patent Act may give rise to prosecution history estoppel, regardless of whether the
amendment was made to avoid prior art, but that such estoppel does not necessarily
bar a suit for infringement against any equivalent to the amended claim element.
The Court noted the difficulty in precisely describing the patent claims which
necessitated the doctrine of equivalents. Patent laws attempt to strike a balance
between the exclusive rights awarded to an inventor for present innovation and the
incentive to others to pursue innovations beyond the scope of the inventor’s exclusive
rights. Therefore, scope of a patent right must be clear so that the public may have
notice of what constitutes an infringement on a patent and what is permissible
innovation. However, language cannot always adequately capture the essence of an
invention. Although the clearest and most certain infringement rule would be
infringement of the literal terms of the patent, such a rule would not necessarily be
the most economically efficient and desirable because it may result in the destruction
of the value of a patent by the availability of equivalents. Therefore, the scope of a
patent is not limited to its literal terms but may include equivalents to the claims


6The notion of an unforeseeability standard for determining whether equivalents
infringement is barred by prosecution history estoppel apparently was advocated in another
amicus curiae brief in Festo and in Matthew J. Conigliaro, Andrew C. Greenberg, & Mark
A. Lemley, Foreseeability in Patent Law, 16 Berkeley Tech. L.J. 1045 (2001).

described. The doctrine of equivalents may create uncertainty and result in more
litigation about the scope of a patent, but it is more equitable toward the inventor
than a literal rule. The Court noted that it had recently affirmed the doctrine of
equivalents in Warner-Jenkinson and had commented in that case that Congress
could legislate the doctrine out of existence at any time.
The Court describes the nature and role of prosecution history estoppel as a
means of ensuring that the doctrine of equivalents remains linked to its underlying
purpose. If the doctrine remedies the inherent limitations of language in adequately
delineating the scope of a patent, then prosecution history estoppel prevents the
inventor from claiming equivalents infringement where the act of making a
narrowing amendment indicates a recognition of the difference between the invention
claim described by the original language and the one described by the amended
language. The patentee has acknowledged that there is no equivalence for
innovations that fall within the scope of the original claim but outside the scope of
the amended claim and the estoppel works to prevent him from regaining through
litigation that which was lost through the application process.
Having reviewed the underlying rationale for the doctrine of equivalents and
prosecution history estoppel, the Court considered the issues presented for
consideration. It noted that although it had made clear that estoppel applies to
amendments made for a “substantial reason related to patentability,” it had not
defined the term nor enumerated reasons, and had even suggested that an amendment
for a reason unrelated to patentability might require estoppel. The Court affirmed the
holding of the CAFC that a narrowing amendment made to satisfy any requirement
of the Patent Act may give rise to estoppel. Although estoppel had been discussed
most often in the context of an amendment to avoid prior art, this did not mean that
estoppel only applied in this context. The underlying rationale, that prosecution
history estoppel rebuts the inference that the proper scope of a patent was
indescribable, still exists where a narrowing amendment made to secure a patent was
for a purpose other than avoiding prior art.
The Court disagreed with the holding of the CAFC that prosecution history
estoppel is a complete bar to equivalents infringement because a complete bar is
inconsistent with the underlying purpose of the doctrine of equivalents and
prosecution history estoppel. A “complete bar” rule would foreclose any
consideration of what subject matter had been surrendered and whether there were
equivalents to the remaining subject matter. The Court noted that even amended
language may not necessarily perfectly capture the essence of an invention and
therefore a patentee should not be restricted to claiming the literal language of a
claim for infringement. A narrowing amendment may indicate what subject matter
was surrendered but not necessarily what remains. The Court affirmed the Warner-
Jenkinson ruling that a patentee has the burden of proving that an amendment was
not made for a reason related to patentability and that where the reason is unclear or
unexplained, the presumption is that the reason was related to patentability and
estoppel applies. The Court then held that the patentee should also bear the burden
of showing that a narrowing amendment for patentability does not surrender the
particular equivalent at issue.



Since the patentee is master of his claim, the presumption is that he knows what
he is surrendering when making a narrowing amendment. However, there may be
reasons why the patentee could not be reasonably expected to have covered the
alleged equivalent in the literal language of a claim, including the unforeseeability
of some equivalents under after-arising technology. This new rule is similar to that
advocated by the Federal Government. Since the record did not clearly show that the
patentee had rebutted the presumption that the surrendered subject matter covered the
disputed equivalent, the case was remanded. One should note that the Court also
criticized the CAFC for disrupting settled expectations regarding the doctrine of
equivalents and prosecution history estoppel and stated that Congress has the
responsibility for changing those well-established principles of patent case law.
Festo-Related Cases
On June 3, 2002, the Supreme Court granted certiorari in nine patent cases, then
vacated prior rulings in those cases and remanded them for further proceedings in
light of its holdings in the Festo case.
Pioneer Magnetics, Inc. v. Micro Linear Corp., ___ U.S. ___, 122 S.
Ct. 2322, 153 L. Ed. 2d 151 (2002). In Pioneer Magnetics, Inc. v. Micro Linear
Corp., 238 F.3d 1341 (Fed. Cir. 2001), the CAFC held that a patentee’s assertion that
it inadvertently narrowed claims in an amendment cannot overcome the presumption
that the amendment was made for reasons of patentability where the amendment was
unexplained in the prosecution history. Pioneer Magnetics filed a petition for
certiorari asking whether a single word that was added inadvertently to a claim
during prosecution without any nexus to a statutory requirement for patentability
automatically gives rise to prosecution history estoppel.
Insituform Technologies v. CAT Contracting, et al., ___ U.S. ___,
122 S. Ct. 2322, 153 L. Ed. 2d 151 (2002). In a non-precedential, unreported
ruling, Insituform Technologies v. CAT Contracting, Inc., 10 Fed. Appx. 871, 58
U.S.P.Q. 2d 1392 (Fed. Cir. 2001), the CAFC held that the “complete bar” rule of
Festo applies retroactively to any open patent case. Insituform Technologies filed a
petition for writ of certiorari, asking whether reasons for a claim amendment during
a prosecution and disclosed in the prosecution history can ever overcome prosecution
history estoppel as a bar to the application of the doctrine of equivalents.
Senior Technologies, Inc. v. R. F. Technologies, Inc., ___ U.S. ___,
122 S. Ct. 2323, 153 L. Ed. 2d 151 (2002). In an unpublished, non-precedential
ruling, Senior Technologies, Inc. v. R.F. Technologies, Inc., 2001 U.S. App. Lexis

4179 (Fed. Cir. March 12, 2001), rehearing denied, 13 Fed. Appx. 930 (Fed. Cir.


2001), the CAFC found that certain claims of the disputed patent had been amended
to overcome a rejection under 35 U.S.C. § 112, the type of amendment which the
Festo petitioners had argued should not trigger estoppel. In accordance with its Festo
ruling, the CAFC held that infringement of the patent under the doctrine of
equivalents was precluded by prosecution history estoppel. Senior Technologies
filed a petition for writ of certiorari, asking, inter alia, whether an amendment that
was editorial and clarifying in nature triggered prosecution history estoppel. The



petitioner alleged that clarifying amendments that did not expressly narrow the
original claim would create estoppel under the CAFC rationale and that issues would
arise as to how trivial an amendment would have to be to not create estoppel.
Creo Products Inc. v. Dainippon Screen Mfg. Co., Ltd., et al., ___
U.S. ___, 122 S. Ct. 2323, 153 L. Ed. 2d 151 (2002). In an unpublished, non-
precedential opinion, Creo Products Inc. v. Dainippon Screen Mfg. Co., Ltd., 10 Fed.
Appx. 921 (Fed. Cir. 2001), the CAFC affirmed the district court’s ruling that
prosecution history estoppel barred application of the doctrine of equivalents to the
disputed patent claim. Creo Products filed a petition for writ of certiorari, asking
whether the case should be remanded for proceedings consistent with the Supreme
Court’s decision in Festo and whether so-called “considerations of fairness” have any
role in the application of the doctrine of equivalents. The petitioner focused on the
fact that the inventor prosecuted the patent application without benefit of an attorney
and amended the claims in accordance with the suggestions of the patent examiner.
The respondent argued that the fact that the examiner suggested the amendments to
an inventor unfamiliar with the legal process was irrelevant; the only relevant fact
under the Warner-Jenkinson ruling was the reason for the amendment, i.e., whether
it was made for reasons related to patentability.
Semitool, Inc. v. Novellus Systems, Inc., ___ U.S. ___, 122 S. Ct.

2323, 153 L. Ed. 2d 152 (2002). In an unpublished, non-precedential opinion,


Semitool, Inc. v. Novellus Systems, Inc.,12 Fed. Appx. 918 (Fed. Cir. 2001), the
CAFC affirmed the lower court’s finding that Semitool had amended a patent
application to narrow a claim to avoid prior art, a reason related to patentability, and
thus held that under the CAFC ruling in Festo, the prosecution history estopped
application of the doctrine of equivalents completely. The CAFC further held that
estoppel also completely barred equivalents infringement for a later patent derived
from the same initial application and containing the same claim limitation as the
amended claim in the earlier patent. Semitool filed a petition for writ of certiorari,
asking “the same question presented in Festo,” whether prosecution history estoppel
completely bars application of the doctrine of equivalents. Semitool argued that
estoppel should only bar the equivalent specifically disclaimed as the difference
between the prior art and its invention and should not bar all other equivalents,
including, allegedly, the invention of Novellus Systems. The respondent argued that
this case concerned prosecution history estoppel based on arguments made by the
petitioner, as well as on amendments made to the claims, as in Festo, but the CAFC
decision could have been based on estoppel by argument alone. Therefore, the
Supreme Court decision in Festo would have no relevance to this case because it only
concerned estoppel by amendment. The petitioner replied that the CAFC explicitly
referred only to estoppel by amendment in its decision and to its Festo decision as the
basis for its decision in this case.
Lockheed Martin Corp. v. Space Systems/Loral, Inc., ___ U.S. ___,
122 S. Ct. 2349, 153 L. Ed. 2d 152 (2002). In Lockheed Martin Corp. v. Space
Systems/Loral, Inc., 249 F.3d 1314 (Fed. Cir. 2001), rehearing en banc denied, 2001
U.S. App. Lexis 16600 (Fed. Cir. June 25, 2001), the CAFC affirmed the lower
court’s decision and held that the narrowing amendment of a claim for reasons
related to patentability (in this case, to distinguish the invention from prior art)
triggered prosecution history estoppel which completely barred a finding of



infringement under the doctrine of equivalents. Lockheed Martin, the patent assignee
and plaintiff, had argued that the addition of a limitation should not bar application
of the doctrine of equivalents for a related, but distinct, original limitation in the
same claim. The CAFC rejected this argument and found that the plaintiff was in
essence arguing for the application of the “flexible bar” rule, which had already been
rejected by the CAFC in Festo. Lockheed Martin filed a petition for writ of certiorari
asking, in addition to the issues presented in Festo, (1) for the judicial basis for
departing from the equitable flexible bar in favor of the absolute bar and (2) whether
the absolute bar applies to equivalents for a limitation in an amended patent claim
which was an original limitation and not the one added by the amendment, although
arguably related to that one. The petitioner argued that the CAFC had gone beyond
its Festo holding in this case.
AccuScan, Inc. v. Xerox Corp., ___ U.S. ___, 122 S. Ct. 2323, 153 L.
Ed. 2d 152 (2002). AccuScan, Inc. v. Xerox Corp., 18 Fed. Appx. 828 (Fed. Cir.

2001), rehearing en banc denied, 2001 U.S. App. Lexis 16640 (Fed. Cir. July 3,


2001), the CAFC reversed the lower court’s decision denying the defendant, Xerox,


a judgment of non-infringement as a matter of law. Upon initial rejection of the
patent application, AccuScan had made arguments distinguishing its claims from
prior art and surrendering the subject matter used by Xerox. Citing Festo, the CAFC
held that, inter alia, prosecution history estoppel precluded a finding of infringement
under the doctrine of equivalents by Xerox. AccuScan filed a petition for writ of
certiorari asking whether the holding of Festo can be expanded to allow claim term
interpretations of non-amending arguments to bar literal patent infringement and to
estop summarily the doctrine of equivalents; whether such summary estoppel adds
significantly to the body of law; and whether unchecked judicial discretion in
summarily applying argument-based claim interpretation to estop the doctrine of
equivalents circumvents the Seventh Amendment right to a jury trial in patent
infringement cases. AccuScan argued that the CAFC had confused and blurred the
line between argument-based claim term interpretation and argument-based
prosecution history estoppel and that the Festo holding did not apply to argument-
based estoppel. Xerox responded that the “complete bar” rule of Festo was not even
applied in this case, but that the CAFC relied on well-established precedent that
AccuScan could not reclaim in litigation subject matter which it had explicitly
surrendered during the patent prosecution. It further argued that the traditional
application of estoppel followed by the CAFC had always been an issue of law for
the judge and not an issue of fact for a jury.
PTI Technologies, Inc. v. Pall Corp. Technologies, Inc., ___ U.S.
___, 122 S. Ct. 2324, 153 L. Ed. 2d 152 (2002). PTI and Pall each sued the
other for patent infringement in different district courts; those cases were
consolidated and the district court granted each summary judgment for non-
infringement of the other’s patent. In Pall Corp. v. PTI Technologies, Inc., 259 F.3d
1383 (Fed. Cir. 2001), the CAFC affirmed the finding of non-infringement for the
PTI patent and remanded the case concerning the Pall patent to resolve issues of
whether certain subject matter may have been disclaimed during patent prosecution.
PTI Technologies filed a petition for writ of certiorari asking whether a finding of
prosecution history estoppel completely bars equivalents infringement for its patent
and asking that if the Supreme Court reversed the CAFC holding in Festo, that it
reverse and remand this case for proceedings consistent with a Festo reversal.



Although it conceded that narrowing amendments had been made, it argued that
Pall’s invention covered unforeseen technological developments which could not
have been surrendered by PTI.; PTI apparently was arguing for a “flexible bar” rule.
Pall responded that this case did not implicate Festo at all, because under well-
established precedents for prosecution history estoppel, PTI had surrendered the
disputed subjected matter in Pall’s invention.
Mycogen Plant Science, et al. v. Monsanto Company, ___ U.S. ___,

122 S. Ct. 2324, 153 L. Ed. 2d 153 (2002). In Mycogen Plant Science, Inc. v.


Monsanto Co., 252 F.3d 1306 (Fed. Cir. 2001), rehearing denied, 261 F.3d 1345
(Fed. Cir. 2001), the CAFC held that cancelling a rejected claim and replacing it with
a new one, as opposed to making a narrowing amendment, would not avoid the
“complete bar” rule announced in Festo. It concluded that a distinction between such
a situation and the narrowing amendments presented in Festo would be one of form,
not of substance. Mycogen filed a petition for writ of certiorari asking, inter alia, (1)
whether a finding of prosecution history estoppel completely bars the application of
the doctrine of equivalents, the same issue presented in Festo and (2) whether
cancelling an independent claim and amending a claim dependent on the cancelled
claim in order to convert it into an independent form justifies a complete bar to
equivalents infringement when the only limitation in the converted, formerly
dependent claim was never amended. Basically, Mycogen seems to argue for a
“flexible bar” rule or alternatively, if a “complete bar” rule had been upheld by the
Supreme Court, that the specific claims for which Monsanto allegedly had
equivalents had never been amended and had not been narrowed.
Other issues. After oral arguments before the Supreme Court in the Festo
case, the parties in Litton Systems Inc. v. Honeywell Inc., No. 00-1617, petition for
certiorari filed, 69 U.S.L.W. 3702 (Apr 23, 2001), agreed to dismiss that case. The
CAFC had held that the “complete bar” rule of Festo precluded application of the
“flexible bar” rule under the doctrine of the law of the case (238 F.3d 1376 (Fed. Cir.
2001)). The “flexible bar” rule had already been applied in an earlier decision in this
particular case. Although the doctrine of the law of the case normally precludes
reconsideration of an issue already decided at an earlier stage of the case, the CAFC
had noted that one exception to this doctrine is where, during the pendency of the
case, controlling authority has issued a contrary rule of law applicable to the issue.
Therefore, the new “complete bar” rule applied, rather than the earlier “flexible bar”
rule. Litton Systems had petitioned the Supreme Court for a writ of certiorari, asking
whether retroactive application of the CAFC Festo rule to this case is contrary to
other decisions allowing a “flexible bar” range of equivalents.
Although the CAFC had intended to increase certainty with its “complete bar”
rule in its Festo decision, the ruling reportedly had the opposite effect in cases
pending before lower federal courts,7 and caused confusion among patent
practitioners, since it had “disrupt[ed] settled expectations.”8 The decision had also
allegedly led to an increase in appeals of rejections during patent prosecutions and


7Lower Courts’ Festo Interpretations Are Increasing Uncertainty, Attorneys Told, 14, No.

4, Software L. Bull. 7 (2001) (citing several cases).


8Festo, 535 U.S. at ___, 122 S. Ct. at 1841, 152 L. Ed. 2d at 960.

increases in claims to avoid amendments.9 Although the affirmation of the “flexible
bar” rule by the Supreme Court may signal a return to prior prosecution strategy and
practice, advocates for a clearer rule may seek a legislative solution, although there
appears to be less support for a sharp limitation of the doctrine of equivalents than
for a continuation of the flexible bar.


9Judge Michel Presses for More Data and Rigor in Patent Reform Process, 63 P.T.C.J. 1565
(2002).