In a highly anticipated decision, the Supreme Court has rejected the Federal Circuit’s standard for indefiniteness – that a claim is indefinite only when it is not amenable to a construction or “insolubly ambiguous” – and replaced it with a new standard requiring that claims must “inform those skilled in the art about the scope of the invention with reasonable certainty.”1 Here we discuss the Supreme Court’s indefiniteness standard from Nautilus and why the Supreme Court has yet again thrown out a long-held Federal Circuit standard.2


Under the Patent Act, a patent specification must “conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as [the] invention.”3 But that was not always the case. In fact, early patents did not even require the inclusion of claims. When Congress passed the Patent Act of 1790, patent applicants merely had to submit a specification, albeit with some specific requirements:

in writing, containing a description… of the thing or things, by him or them invented or discovered, and described as aforesaid, in the said patents; which specification shall be so particular, and said models so exact, as not only to distinguish the invention or discovery from other things before known and used, but also to enable a workman or other person skilled in the art or manufacture, whereof it is a branch, or wherewith it may be nearest connected, to make, construct, or use the same, to the end that the public may have the full benefit thereof, after the expiration of the patent term[.]

Determining what was, and was not, covered by a patent specification was not easy, and thus patents came to include "claims" that defined the metes and bounds of the invention. As the Court recounts, 80 years after the original Patent Act of 1790, Congress passed the Patent Act of 1870, requiring patent applicants to "particularly point out and distinctly claim the part, improvement, or combination which [the inventor] claims as his invention or discovery."4 This requirement, which has been coined "definiteness," has changed little since then and remains an important check on patent applicants; if a claim does not satisfy the definiteness requirement of section 112, then it is invalid. 35 U.S.C. § 282.


Through the years, the process for evaluating whether a claim satisfies the definiteness requirement of 35 U.S.C. 112 has been formalized into a series of considerations. First, "definiteness is to be evaluated from the perspective of someone skilled in the relevant art" at the time that the patent application was filed.5 Moreover, the claims are not read in a vacuum, but in light of the patent’s specification and prosecution history.6

The Court recognizes that evaluating claims for compliance with section 112, entails a “delicate balance.”7 On the one hand, there are “inherent limitations of language” and the uncertainty resulting therefrom is the “price of ensuring the appropriate incentives for innovation.”8 And patents are “not addressed to lawyers, or even to the public generally,” but to “those skilled in the relevant art.”9

On the other hand, “a patent must be precise enough to afford clear notice of what is claimed, thereby apprising the public of what is still open to them.”10 A lack of clear notice results in a “zone of uncertainty which enterprise and experimentation may enter only at the risk of infringement claims.”11 And this zone of uncertainty may create “powerful incentives” for patent applicants “to inject ambiguity into their claims.”12


For years, the Federal Circuit has held that patent applicants satisfy the definiteness requirement as long as the claim is “amenable to construction,” and the claim, as construed, is not “insolubly ambiguous.”13Thus, in this delicate balance, the Federal Circuit gave the benefit of the doubt to patent holders.

The dispute between Biosig and Nautilus began in the 1990s when Biosig allegedly disclosed its patented heart-rate monitor technology to Nautilus’ predecessor-in-interest, StairMaster.14 After StairMaster allegedly began selling unlicensed infringing devices, Biosig filed suit in 2004.15 Biosig’s patent was then thrown into reexamination, during which Biosig submitted a declaration from the inventor touching on the sufficiency of the written specification.16 The declaration stated, among other things, that although certain aspects of the invention could not be standardized amongst exercise machines “a skilled artisan could undertake a ‘trial and error’ process” of experimentation to determine whether a device satisfied an element of the Biosig patent.17

After emerging from reexamination in 2010, the infringement suit began again.18 During claim construction, Biosig and Nautilus proposed different constructions for the term “in spaced relationship with each other.”19 The district court accepted neither construction, instead arriving at its own definition: “there is a defined relationship between the live electrode and the common electrode on one side of the cylindrical bar and the same or a different defined relationship between the live electrode and the common electrode on the other side of the cylindrical bar.”20 Based on that construction, Nautilus moved for summary judgment that the term was indefinite.21 Although the Court had been able to construe the term, and thus the term could not be “insolubly ambiguous,” the Court granted Nautilus’ motion and declared that the term “spaced relationship” was indefinite.22 Reasoning that the term “did not tell the court or anyone what precisely the space should be, or even supply any parameters for determining the appropriate spacing,” the District Court was essentially applying a standard that seems to align with the Supreme Court’s decision: even when a construction is possible, if a potential infringer cannot be reasonably certain what the claim means or covers, then the claim is indefinite.23

On appeal, the Federal Circuit majority opinion held that, based on the statements during reexamination, “a skilled artisan would know that she could attain the indicated functions of [the claims] by adjusting design variables, including spacing.”24 Accordingly, the Federal Circuit reversed and remanded because a claim is indefinite “only when it is not amenable to construction or insolubly ambiguous.”25


On review, the Supreme Court found that the Federal Circuit’s test struck the wrong balance. The Court particularly noted that the temptation for patent applicants to inject ambiguity into their claims should be eliminated and at the same time, the patent drafter has the most power to resolve ambiguity.26 According to the Court, by applying the correct balance, 35 U.S.C. § 112 ¶ 227should be read “to require that a patent’s claims, viewed in light of the specification and prosecution history, inform those skilled in the art about the scope of the invention with reasonable certainty.”28 This standard, the Court held, “mandates clarity, while recognizing that absolute precision is unattainable.”29

But what was wrong with the old standard? The Court held that “[i]t cannot be sufficient that a court can ascribe some meaning to a patent’s claims; the definiteness inquiry trains on the understanding of a skilled artisan at the time of the patent application, not that of a court viewing matters post hoc.”30 And if a claim can be imprecise “just short” of being “insolubly ambiguous,” the Court reasoned that the definiteness requirement’s public-notice function would be thwarted and the “innovation-discouraging zone of uncertainty” would be fostered.31 Ultimately, the Court described the Federal Circuit’s old standard as “leav[ing] courts and the patent bar at sea without a reliable compass.”32


The decision leaves many questions unanswered: Now that we have a new standard, how will it be applied? What does it mean that a “patent’s claims, viewed in light of the specification and prosecution history, [must] inform those skilled in the art about the scope of the invention withreasonable certainty?” What is “reasonable certainty?” How reasonable must alternate possible constructions be before there is no certainty? Is the boundary between definite and indefinite any more clear than before? Will this just become another battle of the experts? And if there is a genuine dispute as to the construction of a claim term, as frequently happens, does that mean that the meaning of the term is not “reasonably certain?”

Although it would be beneficial if the Court would provide guidance on how it wants the new “reasonable certainty” standard to be applied, in this case, the Court “decline[d] to apply the standard” to resolve the controversy between Nautilus and Biosig. Instead, the case has been remanded to the Federal Circuit for further proceedings and patent holders and accused infringers alike will be watching the Federal Circuit with interest for the resolution of Nautilus.