Anyone seeking U.S. patent protection should take notice of a recent Federal Circuit decision governing the standard of clarity required for patent claims proffered in the U.S. Patent and Trademark Office (PTO). In re Packard, No. 2013-1204 (Fed. Cir. May 6, 2014), places the court’s approval on the PTO’s practice of rejecting claims that contain “words or phrases whose meaning is unclear.” Clarity, or definiteness, in patent claims has been the subject of considerable recent commentary, and the Packard decision should complement an impending Supreme Court decision that is expected to resolve closely related definiteness questions.

Under 35 U.S.C. § 112(b), a patent claim must particularly point out and distinctly claim the subject matter which the inventor or a joint inventor regards as the invention. As courts have explained, the statutory definiteness requirement functions to screen out claims cast in ambiguous, vague, or indefinite terms so that the public can discern the boundaries of a patent owner’s exclusive rights. Substantive standards have been set forth for determining indefiniteness of claims in an issued patent, but the Federal Circuit had never before defined the proper standard to be used during patent examination.

In Packard, the PTO rejected all of the applicant’s proposed claims as indefinite during patent prosecution. The applicant appealed, arguing that the oft-cited and relatively forgiving “insolubly ambiguous” standard controls all indefiniteness inquiries, whether directed to an issued patent in litigation or pending patent claims in the PTO. Accordingly, the applicant claimed that the PTO erred by applying its more exacting “unclear meaning” standard pursuant to MPEP § 2173.05(e).

The Federal Circuit concluded that the PTO used the correct definiteness standard for patent prosecution. Emphasizing that patent prosecution differs from post-issuance inquiries in that the applicant can still clarify indefinite claim language by amendment, the court held that the PTO need only issue “a well-grounded rejection that identifies ways in which language in a claim is ambiguous, vague, incoherent, or otherwise unclear,” which then shifts the burden to the applicant to offer a satisfactory amendment or persuasive explanation of why the language is not unclear. Because the applicant in Packard failed to provide a thorough and persuasive response focused on the claims, the PTO’s rejection was upheld.

The court took great pains, both in the panel opinion and in a lengthy concurrence by Judge S. Jay Plager, to emphasize that it was reaching only the issue of indefiniteness in pre-issuance PTO proceedings, noting that the Supreme Court’s forthcoming decision in Nautilus, Inc v. Biosig Instruments, Inc. will resolve the related standard for indefiniteness as to issued patent claims.