Inter partes reexamination was replaced by IPR on September 16, 2012. New requests are no longer accepted. Current proceeding: Inter Partes Review (IPR).
Pre-AIA Patent Proceedings
Inter Partes Reexamination
The pre-AIA patent challenge that became IPR — and why its estoppel was its downfall.
Quick Answer
Inter partes reexamination allowed third-party participation in USPTO patent challenges — but its broad estoppel (blocking all invalidity grounds the requester could have raised in any later litigation) made it a trap. The AIA replaced it with IPR in 2012, offering a faster, trial-like proceeding at PTAB with a 12-month statutory timeline.
Comparison
Inter Partes Reexam vs. IPR — Key Differences
| Inter Partes Reexam (pre-2012) | Inter Partes Review (IPR, current) | |
|---|---|---|
| Status | Abolished September 16, 2012 | Current — active proceeding |
| Forum | USPTO examination corps (examiner) | PTAB — panel of 3 APJs (trial proceeding) |
| Institution threshold | Substantial new question of patentability (SNQ) — low bar | Reasonable likelihood petitioner prevails on ≥1 claim — higher bar |
| Grounds | §§ 102/103 patents and printed publications only | §§ 102/103 patents and printed publications only |
| Timing limit | No filing deadline after grant | Within 1 year of service of infringement complaint |
| Timeline | 2–6+ years (notorious backlog) | 12 months from institution (statutory); extendable 6 months |
| Requester participation | Throughout — requester responds to patent owner | Throughout — petitioner files briefs, has oral argument |
| Standard of review | Preponderance (substantial new question for institution) | Preponderance of evidence |
| Estoppel scope | Raised or could have raised — ANY claim or defense in ANY court | Raised or reasonably could have raised in IPR |
| Appeal path | BPAI → Federal Circuit (slower) | PTAB → Federal Circuit (direct) |
| Cost | $8,800 filing fee + legal costs | $19,000–$25,000 + legal costs |
FAQ
What is inter partes reexamination?
Inter partes reexamination was a USPTO administrative proceeding (35 U.S.C. §§ 311–318, pre-AIA) that allowed a third party to request reexamination of an issued patent based on prior art patents or printed publications. Unlike ex parte reexamination (where the requester has limited participation after filing), inter partes reexamination allowed the requester to participate throughout — responding to the patent owner's arguments and filing appeals. The AIA replaced inter partes reexamination with inter partes review (IPR), effective September 16, 2012.
When did inter partes reexamination end?
The AIA abolished inter partes reexamination for patents that received an inter partes reexamination request on or after September 16, 2012. After that date, the new proceeding is inter partes review (IPR) before the Patent Trial and Appeal Board (PTAB). Pending inter partes reexaminations that were initiated before September 16, 2012 continued to proceed to conclusion under the old rules. Some legacy proceedings remained ongoing for years after the AIA's effective date.
What was the estoppel from inter partes reexamination?
Inter partes reexamination created a two-level estoppel that made it very risky for defendants: (1) during reexamination, the requester was estopped from asserting invalidity in district court on any ground the requester RAISED OR COULD HAVE RAISED during reexamination; (2) after a final decision adverse to the requester, the requester was estopped from raising in subsequent litigation any issue actually decided adversely in the reexamination. This broad estoppel significantly deterred use — a requester who lost risked being barred from ALL invalidity arguments in subsequent litigation.
How does IPR differ from the old inter partes reexamination?
Key differences: (1) INSTITUTION THRESHOLD — inter partes reexam required only a 'substantial new question of patentability' (SNQ); IPR requires 'reasonable likelihood that the petitioner would prevail' on at least one challenged claim — higher bar; (2) TIMING — inter partes reexam had no filing deadline after grant; IPR must be filed within 1 year of being served with an infringement complaint; (3) FORUM — inter partes reexam was conducted by an examiner in the patent examination corps; IPR is a trial proceeding before a panel of Administrative Patent Judges (APJs) at PTAB; (4) TIMELINE — inter partes reexam was notoriously slow (2–6+ years); IPR has a statutory 12-month timeline from institution to final written decision; (5) ESTOPPEL — IPR estoppel applies to grounds raised or 'reasonably could have raised'; same scope.
Can inter partes reexamination still be filed today?
No — inter partes reexamination cannot be initiated for any request filed after September 16, 2012. The current analogous proceeding is inter partes review (IPR) before PTAB. For patents that cannot be challenged via IPR (e.g., because the challenger missed the 1-year deadline after a complaint), ex parte reexamination remains available (no timing bar, no estoppel, but requester has limited participation and cannot pursue the invalidity theory simultaneously in court without estoppel risk).
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