In post-patent issuance proceedings before the US Patent and Trademark Office (USPTO) – inter partes review (IPR), covered business method (CBM), and post-grant review (PGR) – parties almost invariably submit expert testimony. Depending on the type of post-issuance proceeding, the testimony can relate to prior art, claim construction, patent-eligibility, or formal requirements for patentability including adequacy of written description, enablement, and definiteness.…