With the much-publicized issue of vague patent claims square in its sights, the United States Supreme Court has issued a new standard by which courts may find patents invalid for indefiniteness. The new standard may give defendants another tool in their arsenal to challenge the validity of patent claims that are not precise or clear.

In Nautilus, Inc. v. Biosig Instruments, the Court addressed the Patent Act's definiteness requirement, which requires a patent to conclude with "claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as the invention." 35 U.S.C. § 112 ¶ 2. Under the prior standard, a claim was indefinite only if it were either "not amenable to construction" or "insolubly ambiguous." Under the new standard, a patent claim is invalid if it fails to "inform those of skill in the art about the scope of the invention with reasonable certainty."

In its opinion, the Court also noted that indefiniteness is to be assessed: (i) from the perspective of someone who is skilled in the relevant art; (ii) in light of the patent's specification and prosecution history; and (iii) as of the time of the patent's filing.

The definiteness requirement has been part of the Patent Act since 1870, and the text quoted above has remained unchanged since 1957. Nonetheless, the Court's opinion shows that its meaning has remained open to dispute. As it has done in so many recent patent cases, the Court's new opinion strikes down a standard set by the Federal Circuit for patents.

The Court found the previous "insolubly ambiguous" standard to be, simply, ambiguous.  One part of the Court decision that may be a key to future indefiniteness cases may be the following text:

It cannot be sufficient that a court can ascribe some meaning to a patent's claims; the definiteness decision trains on the understanding of a skilled artisan at the time of the patent application, not a court viewing matters post hoc. To tolerate imprecision just short of that rendering a claim 'insolubly ambiguous' would diminish the definiteness requirement's public-notice function and foster the innovation discouraging 'zone of uncertainty' against which this Court has warned.

Whether the new standard is actually more precise than the previous one remains to be seen as it is applied to specific claims, including the claims in this case on remand.

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