Examining The Level Of Detail Required To Plead A Claim Under The Doctrine Of Equivalents

Patentees face many challenges in trying to prove literal infringement, particularly when dealing with competitors who make trivial modifications or superficial changes to the patented invention. In such situations, the doctrine of equivalents plays an important role in buttressing the scope of protection afforded by a patent and in preventing subversion of valuable rights through what amounts to nothing more than a misappropriation in disguise. At the pleading stage, patentees often attempt to avoid early dismissal by pleading infringement under the doctrine of equivalents, either alone or as an alternative to literal infringement. The question then becomes what is required to adequately plead a DOE claim.

Since the general change in pleading standards (discussed in more detail below), the Federal Circuit has not directly articulated the specificity of factual allegations required to state a plausible claim for patent infringement under the doctrine of equivalents ("DOE"). Some Federal Circuit cases require only a cursory allegation of infringement under the DOE while others require factual allegations to support equivalency under the function-way-result test or the insubstantial differences test.¹ And there is no consensus among district courts either.² Understanding the level of detail required to be pled in a complaint for patent infringement is essential for plaintiffs seeking to mitigate the risk of an early dismissal and for defendants seeking to determine whether it is worth the time and expense to challenge the sufficiency of a complaint early in the case.

The DOE is a judicially created doctrine that prevents an accused infringer from skirting liability for infringement by simply changing minor or insubstantial details of a claimed invention to take the accused product or activity outside the scope of literal infringement. Pursuant to the DOE, 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." "A finding of infringement underthe doctrine of equivalents requires a showing that the difference between the claimed invention and the accused product or method was insubstantial or that the accused product or method performs the substantially same function in substantially the same way with substantially the same result as each claim limitation of the patented product or method."³ The DOE is not applied to the invention as a whole but to individual elements of a claim on a limitation-by-limitation basis.⁴

It is well established that particularized evidence is required to support a jury verdict for patent infringement based on DOE.⁵ However, to reach trial, a patentee must first overcome dismissal at the pleading stage by pleading sufficient factual allegations. For claims of patent infringement under the DOE, questions remain regarding what level of factual allegations are sufficient to avoid dismissal.

This inquiry is somewhat complicated by the relatively recent shift in pleading standards applicable to virtually all federal civil cases, including patent infringement cases.In the past, a patentee could state a viable claim for direct patent infringement by compliance with Form 18, as authorized by former Federal Rule of Civil Procedure 84. As explained by the Federal Circuit, Form 18 required only "(1) an allegation of jurisdiction; (2) a statement that the plaintiff owns the patent; (3) a statement that defendant has been infringing the patent 'by making, selling, and using [the device] embodying the patent'; (4) a statement that the plaintiff has given the defendant notice of its infringement; and (5) a demand for an injunction and damages."⁶ However, in September 2014, the Judicial Conference of the United States voted to abrogate Rule 84 and the accompanying appendix of forms, including Form 18, and the abrogation took effect on December 1, 2015.⁷ After this abrogation, the Federal Circuit and district courts apply the pleading standard set forth by the Supreme Court in Twombly and Iqbal to claims for patent infringement.⁸ Under this standard, a complaint must "contain sufficient factual matter, accepted as true, to 'state a claim to relief that is plausible on its face.'"⁹ "A claim has facial plausibility when the plaintiff pleads factual content that allows the court to draw the reasonable inference that the defendant is liable for the misconduct alleged."¹⁰ More is required than mere "labels and conclusions," and "a formulaic recitation of the elements of a cause of action will not do."¹¹

The Federal Circuit has given some guidance on the level of factual support a patentee must plead to state a plausible claim for patent infringement under the Twombly/Iqbal standard. For example, the Federal Circuit has explained that a patentee is not required to plead infringement on an element-by-element basis, and that it is enough that a complaint place the alleged infringer on notice of what activity is being accused of infringement.¹² Moreover,the Federal Circuit has explained that the level of detail required to state a plausible claim for patent infringement under Twombly/Iqbal "'depend[s] upon a number of factors, including the complexity of the technology, the materiality of any given element to practicing the asserted claim(s), and the nature of the allegedly infringing device.'"¹³ Although detailed factual allegations may not always be required, "a plaintiff cannot assert a plausible claim for infringement under the Iqbal/Twombly standard by reciting the claim elements and merely concluding that the accused product has those elements."¹⁴ Instead, "[t]here must be some factual allegations that, when taken as true, articulate why it is plausible that the accused product infringes the patent claim."¹⁵

The Federal Circuit's guidance, however, does not settle the question on the amount of detail required in factual allegations under the DOE. So, while the same Twombly/Iqbal standard applies,¹⁶ the application of this standard in practice remains unsettled.

District courts are split on the amount of detail required in pleading a DOE claim. Some courts have held that a patentee need not explicitly plead infringement under the DOE and that a DOE claim can be brought through an allegation of direct infringement.¹⁷ This approach does not seem consistent with the requirement that the complaint must provide the defendant with notice of what activity is being accused of infringement. District courts within the Ninth Circuit take the view that if a plaintiff plausibly alleges literal infringement, general allegations of infringement under the DOE are sufficient.¹⁸ This approach makes some sense because it allows for the possibility that evidence gathered during discovery reveals that there is equivalency but not literal infringement.¹⁹ Other district courts have required a higher level of detail in pleading a claim under the DOE. For example, in Midwest Athletics and Sports Alliance LLC v. Xerox Corporation, the court explained that "[t]he technical and factual nature of an infringement claim under the doctrine of equivalents requires some level of specificity beyond a one-sentence accusation" and that "plausibility requires sufficient allegations to allow the Court to infer an accused product performs substantially the same function in substantially the same way to obtain the same result as a patent-in-suit."²⁰

Although the Federal Circuit has not explicitly adopted a requirement that a higher level of detail is required to plead a DOE claim, at least one judge on the Federal Circuit bench believes this should be the law.²¹ In McZeal, Judge Dyk dissented from the majority's decision to vacate the lower court's dismissal of the plaintiff's DOE claim, explaining that to provide meaningful notice to the defendant as to limitations allegedly infringed under the doctrine of equivalents, the plaintiff must specify "how the accused product is insubstantially different from the patented devices."²² Judge Dyk also cited the court's treatment of DOE claims in the summary judgment context, where the court requires the patentee to prove infringement on a limitation-by-limitation basis by submitting particularized testimony to create an issue of material fact, and argued that this precedent "underscore[s] the need to supply some specificity in both alleging and proving a doctrine of equivalents claim."²³

The view endorsed by Judge Dyk is not inconsistent with Federal Circuit precedent.For example, in Nalco Co. v. Chem-Mod, LLC, the Federal Circuit found the complaint's "detailed infringement contentions explaining its doctrine of equivalents claim" sufficiently stated a claim under the DOE where the allegations detailed how defendant's method performed substantially the same function, in the same way with the substantially same result as the "injecting" claim element.²⁴ Additionally, the Federal Circuit has adopted the view that the level of detail required to state a claim for patent infringement will vary depending on a number of factors. Potentially, then, one factor which may require a higher level of detail is whether the patentee's claim is brought under the doctrine of equivalents.

To mitigate the risk of early dismissal at the Rule 12 stage, a patentee should identify in its complaint which claim limitations it believes are met via equivalents and include enough factual content in the complaint to allow the court to infer that the accused product or process plausibly contains substantial equivalents to those specific claim limitations. Relatedly, a defendant accused of infringement under the doctrine of equivalents should consider challenging the sufficiency of the patentee's allegations via a motion to dismiss where the complaint lacks factual content explaining how the accused instrumentality contains equivalents to specific elements of the asserted claims. As it currently stands, the amount of factual allegations required to sufficiently plead a DOE claim will likely depend largely on the district court deciding the case.

Footnotes

1 Compare Disc Disease Sols. Inc. v. VGH Sols., Inc., 888 F.3d 1256, 1260 (Fed. Cir. 2018)(finding plaintiff's DOE claims sufficient in a case involving "simple technology" where plaintiff alleged the accused products met every limitation either literally or equivalently and attached photos of the accused products to the complaint) with Nalco Co. v. Chem-Mod, LLC, 883 F.3d 1337, 1354 (Fed. Cir. 2018)(finding plaintiff's DOE claims sufficient where the allegations detailed how defendant's method performed substantially the same function, in the same way with the substantially same result as claim element).

2 Compare Tigo Energy Inc. v. SunSpec All., 679 F. Supp. 3d 947, 959 (N.D. Cal. 2023) ("[I]f a plaintiff plausibly alleges literal infringement, general allegations of infringement under the doctrine of equivalents suffice[]") with SIPCO, LLC v. Jasco Prods. Co., LLC, No. CIV-19-00709, 2022 WL 610192, at *4 (W.D. Okla. Mar. 1, 2022) (requiring plaintiff to plead facts specifying "in what way [defendant's] accused products infringe the relevant claims under the doctrine of equivalents, or otherwise drop the contention").

3 AquaTex Indus., Inc. v. Techniche Sols., 479 F.3d 1320, 1326 (Fed. Cir. 2007).

4 NexStep, Inc. v. Comcast Cable Commc'ns, LLC, 119 F.4th 1355, 1370 (Fed. Cir. 2024), cert. denied, 145 S. Ct. 2794 (2025).

5 To support a claim for patent infringement under the DOE at trial, the patentee must present "particularized testimony and linking argument as to why the function, way and result of each element in the accused devise is substantially the same as the elements of the claimed invention. Generalized testimony concerning the similarities between the claims and the accused device and evidence or argument subsumed in a plaintiff's case of literal infringement are insufficient to establish infringement under the doctrine of equivalents. Rather, a plaintiff must articulate the comparison between the claimed elements and the elements of the accused device and present substantial evidence comparing the claimed elements and the accused device in each of the three aspects of equivalency, i.e. the function, way, and result inquiry." LifeScan, Inc. v. Home Diagnostics, Inc., 103 F. Supp. 2d 345, 360 (D. Del. 2000), aff'd, 13 F. App'x 940 (Fed. Cir. 2001) (internal citations and quotations omitted).

6 In re Bill of Lading Transmission & Processing Sys. Pat. Litig., 681 F.3d 1323, 1334 (Fed. Cir. 2012).

7 See Supreme Court of the United States, Order Regarding Amendments to the Federal Rules of Civil Procedure (Apr. 29, 2015), https://www.supremecourt.gov/orders/courtorders/frcv15(update)_1823.pdf.

8 See, e.g., Bot M8 LLC v. Sony Corp. of Am., 4 F.4th 1342, 1352-53 (Fed. Cir. 2021).

9 Ashcroft v. Iqbal, 556 U.S. 662, 678, (2009) (quoting Bell v. Twombly, 550 U.S. 544, 570 (2007)).

10 Iqbal, 556 U.S. at 678.

11 Bot M8, 4 F.4th at 1353 (quoting Twombly, 550 U.S. at 555).

12 Id. at 1352.

13 Id. at 1353.

14 Id.

15 Id.

16 "In determining what should be required in a patent-infringement pleading under the doctrine of equivalents, a court should begin with the two Iqbal principles," namely, the plaintiff should plead objective facts that the court will take as true, and the allegations must rise to the level of a facially plausible claim for relief. Richard A. Kamprath, Patent Pleading Standards After Iqbal: Applying Infringement Contentions As A Guide, 13SMU Sci. & Tech. L. Rev. 301, 315 (2010). See Vytacera Bio, LLC v. CytomX Therapeutics, Inc., No. CV 20-333-GBW-CJB, 2023 WL 7125196, at *5 (D. Del. Oct. 30, 2023), report and recommendation adopted in part, No. CV 20-333-JLH-CJB, 2024 WL 4512400 (D. Del. Oct. 17, 2024) ("[There is nothing magical about a claim of direct patent infringement pursuant to the DOE that suggests that it should be treated differently for pleading purposes than any other type of claim under the law.")

17 Gracenote, Inc. v. Sorenson Media, Inc., 2017 WL 2116173 at *4 (D. Utah May 15, 2017).

18 See Tigo Energy, 679 F. Supp. 3d at959 (compiling cases).

19 See, e.g., Intrepid Automation, Inc. v. 3D Sys., Inc., No. 24-CV-2262-AGS-DDL, 2025 WL 1940192, at *2 (S.D. Cal. July 15, 2025).

20 2018 WL 1400426, *4 (D. Neb. 2018) (further stating that for a DOE claim, "[b]are infringement allegations, unsupported legal conclusions, and formulaic recitations of the elements of infringement are insufficient."); see also SIPCO, LLC v. Jasco Prods. Co., LLC, No. CIV-19-00709, 2022 WL 610192, at *4 (W.D. Okla. Mar. 1, 2022) (holding that to comply with relevant pleading standards, the plaintiff must plead facts to specify "in what way [defendant's] accused products infringe the relevant claims under the doctrine of equivalents, or otherwise drop the contention").

21 McZeal v. Sprint Nextel Corp., 501 F.3d 1354, 1359 et seq. (Fed. Cir.2007) (Dyk, J., concurring in part and dissenting in part).

22 Id. at 1361 (Dyk, J., concurring in part and dissenting in part).

23 Id. at 1363 (Dyk, J., concurring in part and dissenting in part).

24 883 F.3d 1337, 1354 (Fed. Cir. 2018).

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