Prior to the US Supreme Court decision on June 2, 2014, the standard for invalidating a claim, in litigation, due to indefiniteness was that the claim had to be not amenable to construction (interpretation). The Supreme Court overturned that standard in Nautilus v. Biosig. In Nautilus v. Biosig, the Supreme Court held that a patent claim can be found to be invalid due to indefiniteness if the claim, read in light of the patent specification and prosecution history, fails to inform, with reasonable certainty, those skilled in the art about the scope of the invention.
The new standard for invalidity due to indefiniteness is very similar to the requirement for indefiniteness during prosecution. A decision on whether a claim is indefinite requires a determination of whether those skilled in the art would understand what is claimed when the claim is read in light of the specification. MPEP 2173.
The impact of Nautilus on prosecution will be the enhanced awareness of indefiniteness. Terms such as “capable of,” and “can be” should be avoided (see Ex Parte Breed PTAB decision of June 4, 2014).
The impact of Nautilus on litigation is harder to assess. It all depends on how the term “with reasonable certainty” is interpreted by the Federal Circuit. Some caution will result from the Supreme Court decision but the fact that the term in question is discussed in a Markman hearing and a claim construction is arrived at, gives some credence to the reasonable certainty. We will have to wait and see, but for sure, indefiniteness will be back in the quiver of tools for invalidity.