Is the Reverse Doctrine of Equivalents Alive and Well (Even if on Life Support)?

Following the Federal Circuit’s decision in Steuben Foods, Inc. v. Shibuya Hoppmann Corp., a concern existed that the reverse doctrine of equivalents (RDOE) was no longer a valid defense to patent infringement.¹ Indeed, after rejecting the defendant’s RDOE defense, the court noted that it had never affirmed a finding of noninfringement based on the RDOE.² Regardless, the RDOE may remain a viable defense that, even if unsuccessful, could influence the court’s ultimate decision. Here, we analyze relevant decisions discussing the RDOE, even those where the defense proved unsuccessful, especially in light of one recent decision where the defense was successful.  

Origins of RDOE

Under the doctrine of equivalents (DOE), a patentee may establish infringement even when the accused product or process does not fall within the literal language of a claim if the differences between the claims and the accused conduct are insubstantial or the accused product performs substantially the same function in substantially the same way to achieve the same result. The RDOE operates in the opposite direction. Under this doctrine, an accused product may avoid literal infringement if a defendant can prove that despite falling within the literal language of the claims, its accused product works in a substantially different way or is based on a substantially different principle. The RDOE thus prevents patentees from extending their patents to cover conduct that merely has the same function as the patented invention.  

History of the RDOE

The RDOE emanates from the Supreme Court’s decision in Boyden Power-Brake Co. v. Westinghouse.³ There, Westinghouse’s patent claimed an emergency automatic-brake mechanism.⁴ Westinghouse sued Boyden for infringement, arguing that Boyden's device copied its patented method of directing compressed air directly to the brake cylinder. Boyden countered by arguing that although its device may have fallen within the literal language of Westinghouse's patent claims, it achieved the same result through a substantially different mechanism.⁵ Boyden therefore argued that literal correspondence with the claims did not warrant a finding of infringement of the invention itself.⁶ Westinghouse, however, emphasized that the patent in-suit was a pioneering invention and was therefore entitled to a broad scope of protection.  

The District Court for the District of Maryland found that Boyden infringed the second claim of the patent, but not the first and fourth claims. Both parties appealed. The appellate court dismissed the finding of infringement by reversing the lower court's decision regarding the second claim, but upholding the decision on the first and fourth claims. Westinghouse filed a writ of certiorari. The Supreme Court affirmed the finding of the appellate court, holding that:

[E]ven if it be conceded that the Boyden device corresponds with the letter of the Westinghouse claims, that does not conclusively settle the question of infringement… The converse is equally true. The patentee may bring the defendant within the letter of his claims, but if the latter has so far changed the principle of the device that the claims of the patent, literally construed, have ceased to represent his actual invention, he is as little subject to be adjudged an infringer as one who has violated the letter of a statute has to be convicted when he has done nothing in conflict with its spirit and intent.⁷

This language set the foundation for the RDOE. Notably, the Court noted that a patent cannot merely cover “a function” even if the invention is a “pioneer.”⁸  

Although Graver Tank Manufacturing v. Linde Air Products Co. is recognized as the seminal decision defending the DOE, the Supreme Court did affirm the continuing validity of the RDOE.⁹ There, the patent claimed an electric welding process and flux compositions. 8FGraver sued Linde Air for patent infringement under the DOE. Linde was accused of substituting manganese silicate for magnesium silicate in its welding flux.¹⁰ The District Court for the Northern District of Indiana found the four flux claims valid and infringed, but held all process claims invalid. Both parties appealed.

The appellate court affirmed the findings of validity and infringement as to the four flux claims, but reversed the district court's invalidity findings, holding the process claims and remaining flux claims valid.¹¹ The defendants then petitioned the Supreme Court, contending not only that the judgement should be reversed, but also that the district court's finding of partial validity should also be overturned and the patent declared entirely invalid and not infringed.

The Supreme Court initially reinstated the district court's decision. On rehearing later, the Court limited its analysis of infringement to the four flux claims and the applicability of the DOE.¹² The Court agreed with the district court that manganese silicate and magnesium silicate were substantially equivalent and concluded that "it is difficult to conceive of a case more appropriate for application of the doctrine of equivalents."¹³ The Court therefore upheld the finding of infringement.

Significantly, however, the Court also recognized the existence of the RDOE, explaining that “the wholesome realism of [the doctrine of equivalents] is not always applied in favor of a patentee but is sometimes used against him. Thus, where a device is so far changed in principle from a patented article that it performs the same or a similar function in a substantially different way, but nevertheless falls within the literal words of the claim, the doctrine of equivalents may be used [in reverse] to restrict the claim and defeat the patentee's action for infringement."¹⁴ Accordingly, the decision once again reaffirmed the viability of the RDOE.  

In Texas Instruments, Inc. v. U.S. International Trade Commission, Texas Instruments alleged a violation of Section 337 of the Tariff Act, asserting that imported portable electronic calculators infringed and that the sale of these products would substantially injure the domestic industry protected by the asserted patent.¹⁵ Texas Instruments argued that its patent represented a pioneering invention and therefore deserved a broader scope of protection, contending that all changes in the accused calculators should be considered as structural and functional equivalents of the claimed product.¹⁶ The International Trade Commission (ITC) rejected these arguments, finding that the patented calculator was not a pioneering invention entitled to expanded protection and found no violation of Section 337. Texas Instruments appealed.

The Federal Circuit affirmed the holding. Although the appellate court criticized portions of the ITC's methodology, noting that it incorrectly analyzed individual structural differences rather than evaluating the accused devices as a whole, the Federal Circuit agreed that substantial evidence supported the finding of noninfringement.¹⁷

More significantly, the court addressed the relationship between the RDOE and literal infringement and stated that "the reverse doctrine of equivalents comes into consideration only when literal infringement is apparent."¹⁸ Because the accused calculators did not literally infringe the asserted claims, the RDOE was inapplicable. Thus, the ITC reaffirmed that the RDOE is not a general defense to infringement, but rather a limitation on liability that may be utilized only to rebut literal infringement.  

In Hilton Davis Chemical Co. v. Warner-Jenkinson Co., another seminal decision regarding the DOE, the asserted patent claimed a dye purification process using a porous membrane at pH levels between 6.0 and 9.0.¹⁹ Hilton sued Warner-Jenkinson for patent infringement under the DOE, alleging that even though its purification mechanism did not fall within the literal language of the patented claims, Warner-Jenkinson's use of a porous membrane at a pH level of 5.0 was an insubstantial deviation from the claimed pH range of 6.0 to 9.0.²⁰ The District Court for the Southern District of Ohio found infringement under the DOE. Warner-Jenkinson appealed, and the Federal Circuit reaffirmed the lower court's decision.

Warner-Jenkinson then filed a writ of certiorari, asking the Supreme Court to consider whether the DOE survived Congress's ratification of the Patent Act of 1952.²¹ Warner-Jenkinson argued that the doctrine was inconsistent with the statutory claiming requirements established by the Act and therefore should no longer be recognized.²² The Supreme Court rejected this argument, holding that if Congress had abolished the DOE and intended such a significant change to patent law, it would have expressed that change in the Act.²³ Although the Court did not directly address the RDOE, by preserving the DOE established in Graver Tank, it effectively preserved the legal framework that supports the RDOE.  

In Tate Access Floors, Inc. v. Interface Architectural Res., Inc., the asserted patent claimed a floor panel design with a specific trim.²⁴ Tate sued, alleging that Interface's floor panels infringed. The District Court for the District of Maryland granted Tate's motion for a preliminary injunction.  

Interface appealed, arguing that Tate failed to show a reasonable likelihood of success on the merits of its infringement claim.²⁵ Interface relied in part on the RDOE, arguing that a finding of literal infringement should not necessarily result in liability and that its products merely "practiced the prior art."²⁶ The Federal Circuit rejected this defense and declined to extend the RDOE to support it.

The court further observed that "[n]ot once has this court affirmed a decision finding noninfringement based on the reverse doctrine of equivalents. And with good reason: when Congress enacted 35 U.S.C. § 112, after the decision in Graver Tank, it imposed requirements for the written description, enablement, definiteness, and means-plus-function claims that are coextensive with the broadest possible reach of the reverse doctrine of equivalents."²⁷  

Nevertheless, the court stopped short of abolishing the doctrine; rather, it described the doctrine as an "anachronistic exception, long mentioned but rarely applied."²⁸ This case reflects the court's skepticism toward the RDOE, suggesting that developments in patent law may have replaced the need for the doctrine and rendered it obsolete. Yet, the RDOE defense survived.  

The asserted patent in DePuy Spine, Inc. v. Medtronic Sofamor Danek, Inc. claimed spinal fixation technology.²⁹ DePuy sued, alleging that Medtronic's polyaxial pedicle screws infringe its patent. Medtronic asserted several defenses, including the RDOE and argued that even if its accused device fell within the literal scope of DePuy's patent claims, it operated on a substantially different principle and therefore did not infringe under the RDOE.

The District Court for the District of Massachusetts rejected Medtronic's defense, concluding that the doctrine was inapplicable because the case involved infringement under the DOE rather than literal infringement.³⁰ Finding that Medtronic had advanced a legally unsupported RDOE defense and had unnecessarily multiplied the proceedings by pursuing it, the district court imposed sanctions against Medtronic and its counsel under 28 U.S.C. § 1927.³¹

Medtronic appealed. The Federal Circuit reversed, holding that the district court erred in sanctioning Medtronic for merely asserting the RDOE. The court explained that although the doctrine is rarely invoked and virtually never sustained, the Supreme Court “has recognized it to be a viable defense, even if it is rarely asserted.”³² Accordingly, Medtronic's attempts to use the RDOE were found not frivolous and thus should not serve as the basis for sanctions. While the Federal Circuit did not ultimately find the RDOE applicable on the facts of the case, it reaffirmed that the doctrine remains a viable defense to literal infringement.  

In Steuben Foods, Inc. v. Shibuya Hoppman Corp., the asserted patents claimed aseptic food-packaging and bottling technology.³³ Steuben sued Shibuya for patent infringement, alleging that Shibuya's P7 aseptic bottling line infringed its patents. The District Court for the District of Delaware found at summary judgement that the accused product literally infringed the claims, but because Shibuya asserted the RDOE, the court denied summary judgement given that Shibuya's defense raised genuine issues of material fact.³⁴

The case proceeded to trial, where the jury found the asserted patents both valid and infringed and awarded Steuben more than $38 million in damages.³⁵ Following the verdict, Shibuya moved for judgement as a matter of law under the RDOE, arguing that although its bottling system fell within the literal language of the claims, it operated on a substantially different principle and therefore did not infringe. The district court agreed, granted judgement as a matter of law of noninfringement, and overturned the jury's infringement verdict.³⁶  

Steuben appealed, arguing that the RDOE did not survive the Patent Act of 1952 and that the district court improperly supplanted the jury's factual findings. Although the Federal Circuit described Steuben's arguments regarding the continued viability of the RDOE as "compelling," it declined to decide whether the doctrine survived the 1952 Patent Act.³⁷

Instead, the court held that substantial evidence supported the jury's rejection of Shibuya's RDOE and that the district court had improperly substituted its own view of the evidence for that of the jury.³⁸ Accordingly, the Federal Circuit reversed the district court's finding of non-infringement and reinstated the jury's infringement verdict. Again, this decision demonstrates that the RDOE defense can be successful.  

In Arbutus Biopharma Corp. v. Moderna, Inc., the asserted patents claimed specific lipid compositions and methods of producing them, respectively.³⁹ Arbutus alleged that Moderna’s nucleic-acid Covid-19 vaccination method infringed these patents.

Arbutus moved to exclude portions of the testimony of Moderna's expert, including his opinions related to the RDOE.⁴⁰ Arbutus argued that the expert’s opinion improperly relied on "unclaimed features" of Moderna’s vaccine and therefore misconstrued the RDOE inquiry.⁴¹  

The District Court for the District of Delaware rejected this argument and explained that the expert had considered those features only after assuming Moderna’s vaccine literally infringed the asserted claims. Thus, rather than importing unclaimed features into the patent claims, he relied on those features to support Moderna's argument that despite its vaccine potentially falling within the literal language of the claims, it had "been so far changed in principle that it performs the same or similar function in a substantially different way."⁴²

The court declined to exclude the expert’s testimony and held that "whether the reverse doctrine of equivalents applies in this case is a question of fact for the jury to decide."⁴³ Accordingly, the district court permitted Moderna to present its RDOE defense at trial.

This case is significant because it reaffirms application of the RDOE ordinarily presents factual questions for a jury rather than issues that may be resolved as a matter of law.

In Maquet Cardiovascular LLC v. Abiomed, Inc., the asserted patent claimed a blood pump that circulates blood when the heart fails to adequately do so.⁴⁴ Maquet sued Abiomed, alleging that Abiomed's Impella heart pumps infringed.

Abiomed moved for summary judgement of non-infringement under the RDOE. Judge Saylor denied the motion, finding that factual disputes required resolution at trial. Although he permitted Abiomed to present this defense to the jury, he cautioned that there was a "substantially heightened possibility" that any judgement based on the doctrine could be reversed on appeal.⁴⁵

Following trial in district court, the jury found that Abiomed’s Impella heart pumps met the literal limitations of the asserted claim, but nevertheless returned a verdict of noninfringement under the RDOE.⁴⁶  

The verdict is notable because it represents one of the most recent and successful applications of the RDOE. It demonstrates that despite the Federal Circuit's skepticism regarding the doctrine's place in modern patent law, the defense remains available to accused infringers and may still prove persuasive to a jury.  

RDOE procedure

An RDOE defense should be asserted early in the proceedings. For example, Judge Gilstrap precluded a defendant from asserting the defense when it was first raised at the close of discovery.⁴⁷

Because the RDOE is an affirmative defense, it would be prudent to assert it in the answer and counterclaims. It should certainly be covered during discovery and in expert reports. Otherwise, it could be waived. The proofs in expert reports and at trial should be guided by the observations of the court in Echometer Co. v. Lufkin Industries:

This affirmative defense applies where a device is so far changed in principle from a patented article that it performs the saine or a similar function in a substantially different way, but nevertheless falls within the literal words of the claim. You must determine, based on all the evidence before you, whether [plaintiff] had proved by a preponderance of evidence that [the accused product] performs the same or similar function of what is claimed, but in a substantially different way.⁴⁸

The RDOE defense may be particularly useful in cases where the plaintiff asserts broad claims covering various methodologies. It may be possible to show that the accused device (or process), although literally covered by the claims, operates in a substantially different manner. Resort to the specification, which illustrates only one function or aspect of the claimed invention, may support the RDOE defense.  

Lastly, the RDOE, even if unsuccessful, may influence a jury’s damages award by demonstrating that differences, ­although not substantial, do exist between the essence of the claimed invention and the accused conduct.  

Conclusion

Over the years, the RDOE has been repeatedly criticized and discounted. A careful review of the case law even when the RDOE was ultimately unsuccessful, shows that the defense has appealed to juries in some instances. Thus, defendants should not overlook the defense when facing a charge of literal infringement.