The Second Look: Inter Partes Review and How the PTAB Reshaped Patent Litigation
By Casey Scott McKay ·
Before 2012 a defendant who thought a patent was invalid had one forum and one standard: a federal jury, clear and convincing evidence, and a trial three years away. Inter partes review created a second look, conducted by patent examiners turned judges, on a preponderance standard, finished in eighteen months. This article explains what inter partes review actually is, what can and cannot be raised in it, how institution works and why the discretionary denial doctrine matters more than the merits in many cases, and what estoppel costs a petitioner who loses. It traces the effect on district court litigation, where the availability of a parallel proceeding changed settlement economics permanently. It closes with the strategic question every accused infringer faces in the first ninety days.
IP and Technology > Patent Litigation | Article | Published 5 September 2025 - Updated 18 January 2026 | Casey Scott McKay - marksy.us
Summary. Before 2012 a defendant who thought a patent was invalid had one forum and one standard: a federal jury, clear and convincing evidence, and a trial three years away. Inter partes review created a second look, conducted by patent examiners turned judges, on a preponderance standard, finished in eighteen months. This article explains what inter partes review actually is, what can and cannot be raised in it, how institution works and why the discretionary denial doctrine matters more than the merits in many cases, and what estoppel costs a petitioner who loses. It traces the effect on district court litigation, where the availability of a parallel proceeding changed settlement economics permanently. It closes with the strategic question every accused infringer faces in the first ninety days.
Keywords: inter partes review, post-grant review, PTAB, patent trial and appeal board, institution decision, one-year bar, estoppel, real party in interest, discretionary denial, prior art patents and printed publications, claim construction at the board, motion to amend, parallel district court litigation, stay pending review, expert declaration, preponderance of the evidence, final written decision, appeal to the Federal Circuit, covered business method, reexamination
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