Indefiniteness In Inter Partes Review: The Existing Quagmire And A Path Forward

Under Section 112(b) of the Patent Act, patent claims must satisfy a definiteness requirement by "pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention."¹ Indefiniteness is intertwined with determining a patent's scope through claim construction.² Because determining the scope of challenged claims is a prerequisite to deciding the issues of anticipation and obviousness raised in an inter partes review ("IPR"),³ indefiniteness lurks in the background of IPR proceedings.⁴ The relevant statutory provision requiring the Patent Trial and Appeal Board (the "Board") to issue a final written decision deciding the patentability of any claim challenged in a petition, Section 318, does not expressly limit the statutory bases on which claims may be invalidated,⁵  suggesting the possibility that the Board could invalidate claims as indefinite in an IPR. Yet the Board has interpreted Section 314, the statutory