Indefiniteness

Overview
Under Section 112, second paragraph of the Patent Act, 35 U.S.C. § 112, claims must “particularly point[] out and distinctly claim[] the subject matter which the applicant regards as his invention.” Otherwise, the claims are invalid on grounds of “indefiniteness.” An indefiniteness standard that weeds out claims reasonably susceptible to multiple interpretations could reduce ambiguity and improve notice in a broad range of settings.

The Federal Circuit requires that claims be “insolubly ambiguous” to be invalid as indefinite. The PTO Board of Patent Appeals and Interferences has adopted a lower threshold of ambiguity, however, by ruling that a claim may be indefinite if it is “amenable to two or more plausible claim constructions.” Miyazaki approaches indefiniteness with a focus on notice. In contrast, the “insolubly ambiguous” standard accepts substantial ambiguity. It preserves claims that require a court to make hard choices among varying interpretations, thereby overstating what marketplace participants are likely to understand. The Miyazaki approach is preferable when implemented during PTO review. In the PTO, indefiniteness rulings promptly add clarity and require only a claim amendment from the applicant.