Definitely Not Indefinite: How the Specification Can Save a Claim from Indefiniteness

Posted by Jen Wang on Feb 9, 2017

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In Sonix Technology v. Publications International, the Federal Circuit applied the Supreme Court’s indefiniteness standard from Nautilus and held seemingly imprecise claim language to be definite.

What This Means to You

  • During application drafting and prosecution, identify potentially vague claim terms and consider using a different term or including examples in the specification.
  • In litigation, experts opining on indefiniteness need to provide support to show that a term is subjective. A simple conclusory statement is insufficient.
  • While this case dealt with the type of indefiniteness in which a claim term seems imprecise on its face, it is also important to watch out for claims that seem precise, but involve different methods of measurement. Such claims could also be vulnerable to an indefiniteness attack.

Case Background

The technology in this case relates to “graphical indicators,” which are images that encode information on the surface of an object, similar to a bar code. In contrast to a conventional bar code, however, the invention in the patent at issue uses “visually negligible” graphical indicators that are either invisible to the naked eye or are otherwise unobtrusive such as not to interfere with the other main information on the surface. One example of a non-invisible but still “visually negligible” graphical indicator is a mosaic of nondescript dots or other patterns that sit in the background of an image, but do not interfere with the text or foreground pictures of the image. 

The issue for the Federal Circuit was to decide whether the term “visually negligible” is indefinite. The standard for indefiniteness was established by the Supreme Court in the Nautilus decision. The Supreme Court stated that, for a claim to be definite, a person skilled in the art reading the claim, the specification and the prosecution history of the patent must be able to determine the scope of the claim with “reasonable certainty.”

Here, the specification included two specific examples of “visually negligible” graphical indicators and also included a paragraph listing “requirements for the graphical indicators being negligible to human eyes.” As an example of one such requirement, the specification states that the indicator must be so small that “human eyes cannot differentiate one graphical indicator from others.”

Decision Analysis

The Federal Circuit held that the term “visually negligible” was definite. The court reasoned that the examples and requirements described in the specification provided sufficient guidance to determine the scope of “visually negligible.” 

The court also detailed additional reasons for its holding. For example, the patent at issue went through two ex parte reexamination proceedings, during which no one involved had any apparent difficulty in determining the scope of “visually negligible.” Similarly, during litigation, the parties’ experts had no difficulty in repeatedly applying the term to prior art references and accused products. In addition, the invalidity contentions of Publications International (the accused infringer) had identified 26 claim limitations to be indefinite, but did not include the term “visually negligible.” In fact, Publications International did not question the clarity of “visually negligible” during the first several years of litigation. Finally, Publications International’s expert opined that the term “visually negligible” was subjective and there was no objective test to define it, but did not provide any basis for his conclusion.


  • Be on the lookout for potentially vague claim terms; they could be susceptible to an indefiniteness attack.
  • On the patentee side, during application drafting and prosecution, consider using a different term entirely. If that is not possible, during specification drafting, consider including examples or other forms of guidance that would help a reader to understand the scope of the term.
  • On the patent challenger side, have a game plan regarding indefiniteness arguments as early as possible. Identify the strongest indefiniteness issues early on and provide as much evidence and reasoning as possible to support an expert’s opinion that a term is subjective.

Wolf Greenfield's CAFC Blog

Here, Wolf Greenfield attorneys summarize and identify key takeaways from recent patent law cases decided by the U.S. Court of Appeals for the Federal Circuit. View past case summaries here.

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This blog is intended to promote thought and debate on developing areas of the law. The opinions, commentary and characterizations of cases provided on this blog are not legal advice and do not represent the opinions of Wolf Greenfield or its clients.