On January 10, 2014, the Supreme Court granted certiorari in Nautilus v. Biosig Instruments (13-369) to decide the proper standard for finding patented claims indefinite under 35 U.S.C. § 112. At issue is whether the Federal Circuit’s construction of § 112, ¶ 2 conflicts with the statute by requiring that a claim be “insolubly ambiguous” before finding the claim indefinite. Stated differently, the Supreme Court will consider whether the “insolubly ambiguous” test is consistent with the statutory requirement of particular and distinct patent claiming.
The statutory provision directed to the ‘definiteness’ requirement is found in 35 U.S.C. § 112, ¶ 2, which requires that “[t]he specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.” The public notice function of the claims requires that “claims delineate the patentee’s right to exclude, [and] the patent statute requires that the scope of the claims be sufficiently definite to inform the public of the bounds of the protected invention, i.e., what subject matter is covered by the exclusive rights of the patent.” Halliburton Energy Servs., Inc. v. M-I LLC, 514 F.3d 1244, 1249 (Fed. Cir. 2008).
The definiteness requirement of 35 U.S.C. § 112 applies both at the USPTO during prosecution of a patent application and in federal courts during litigation of a granted patent. However, claims under examination in the Patent Office are evaluated under a different standard than patented claims before a federal court. One of the main reasons for this disparity is because patented claims have are presumed to be valid under 35 U.S.C. § 282.
The Federal Circuit has stated that a claim is indefinite only when it is “not amenable to construction” or “insolubly ambiguous.” Datamize, LLC v. Plumtree Software, Inc., 417 F.3d 1342, 1347 (Fed. Cir. 2005); see also Star Scientific, Inc. v. R.J. Reynolds Tobacco Co., 537 F.3d 1357, 1371 (Fed. Cir. 2008) (“if reasonable efforts at claim construction result in a definition that does not provide sufficient particularity and clarity to inform skilled artisans of the bounds of the claims, the claim is insolubly ambiguous and invalid for indefiniteness”).
In contrast, during prosecution, the U.S. Patent Office interprets claims in the broadest reasonable manner and will find a claim indefinite when it is open to more than one reasonable interpretation. See Ex parte Miyazaki, 89 USPQ2d 1207, 112 (Bd. Pat. App. & Int. 2008). The different threshold for claims under examination is based on a patent record that is still in development and the applicant's ability to amend claims to overcome an indefiniteness rejection. See, e.g., MPEP 2173. In other words, while the threshold for finding a claim indefinite may be lower, a patent applicant has the flexibility to address indefiniteness problems by argument or amendment.
If the Supreme Court ultimately rejects the Federal Circuit’s “insolubly ambiguous” test, one can assume it is because the Court believes the test fails to serve the public notice function of patent claims, especially when ambiguous claim language is insufficient to render a claim insolubly ambiguous. However, it is not clear whether, or how far, the Court might lower the threshold. While the Court could adopt the test set forth in Ex parte Miyazaki, this result seems somewhat unlikely because a patent challenger can almost always find an expert that will present a “reasonable” alternative interpretation of a claim. Under Miyazaki, the claim could then be found invalid.
Multiple tests have been suggested by amici in briefs to the Court. For example, amici Public Knowledge, and The Electronic Frontier Foundation filed October 23, 2013, suggest that the “insolubly ambiguous” test be replaced with a standard requiring that “patent claims must allow a person of ordinary skill in the art to read and understand both what is claimed and what is not claimed.” Br. 16. However, this seems to be more of a goal than a workable test for determining validity of individual claims under 35 U.S.C. § 112.
A decision is expected to be rendered towards the end of the Supreme Court’s term.
 Paragraph 2 of 35 U.S.C. § 112 was replaced with newly designated § 112(b) when the Leahy-Smith America Invents Act (“AIA”) took effect on September 16, 2012. However, the pre-AIA version of § 112 applies in Nautilus because the patent-in-suit issued prior to that date. 35 U.S.C. § 112(b) states in part that “[t]he specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.”
 The Federal Circuit may extend the reach of Ex parte Miyazaki to post-grant proceedings. See In re Packard, Fed. Cir. 2013-1204 (Awaiting decision (argument December 4, 2013)). This would lead to significant uncertainty for patent owners, particularly in a Post-Grant Review proceeding, where the patentee does not have the right to amend the claims (instead, permission is required from the PTAB).