⚖️ Overview: Challenging Issued Patents
After a patent is granted, third parties can challenge its validity through post-grant proceedings at the USPTO. The available procedures depend on when the patent application was filed and what type of prior art you're using.
🎯 Key Rule for Patent Bar:
The patent's effective filing date determines which proceedings are available:
- Before March 16, 2013 = Pre-AIA patent → Ex parte reexam or Inter partes reexam
- On/after March 16, 2013 = AIA patent → Ex parte reexam, IPR, or PGR
📊 Quick Comparison Table
| Proceeding |
Available For |
Timing |
Grounds |
Statute |
| Ex Parte Reexamination |
ALL patents (pre-AIA and AIA) |
Anytime during patent term |
§ 102/103 based on patents or printed publications only |
35 USC § 302 |
| Inter Partes Reexamination |
Pre-AIA patents ONLY (filed before March 16, 2013) |
Anytime during patent term |
§ 102/103 based on patents or printed publications only |
35 USC § 311 (old) |
| Inter Partes Review (IPR) |
AIA patents ONLY (filed on/after March 16, 2013) |
9 months after grant OR after PGR window closes |
§ 102/103 based on patents or printed publications only |
35 USC § 311 |
| Post-Grant Review (PGR) |
AIA patents ONLY (filed on/after March 16, 2013) |
Within 9 months after grant |
ANY ground (§ 101, 102, 103, 112, etc.) |
35 USC § 321 |
1️⃣ Ex Parte Reexamination
Statute: 35 USC § 302
Availability: ALL patents (both pre-AIA and AIA)
Timing: Anytime during the patent term
Who can request: Anyone (including anonymous requests)
Grounds: § 102 (novelty) or § 103 (obviousness) based on patents or printed publications ONLY
⚠️ Key Limitation: Cannot use public use, on-sale, or other non-documentary prior art
How it works:
- Requester files a request with prior art
- USPTO decides whether to grant reexamination (substantial new question of patentability)
- If granted, patent owner and examiner conduct the reexam (requester has limited involvement)
- Proceeding is ex parte = one-sided, like original examination
2️⃣ Inter Partes Reexamination (OBSOLETE)
Statute: 35 USC § 311 (pre-AIA version)
Availability: Pre-AIA patents ONLY (filed before March 16, 2013)
Timing: Anytime during the patent term
Grounds: § 102/103 based on patents or printed publications ONLY
🚫 REPLACED BY IPR: Inter partes reexamination was replaced by Inter Partes Review (IPR) for AIA patents. It still exists for pre-AIA patents but is rarely used.
How it works:
- Similar to ex parte, but requester participates throughout
- More adversarial process
- Patent owner and requester both submit arguments
3️⃣ Inter Partes Review (IPR)
Statute: 35 USC § 311
Availability: AIA patents ONLY (filed on/after March 16, 2013)
Timing: 9 months after grant OR after PGR window closes (whichever is later)
Who can request: Anyone (except the patent owner)
Grounds: § 102 (novelty) or § 103 (obviousness) based on patents or printed publications ONLY
✅ MOST COMMON FOR AIA PATENTS: IPR is the go-to proceeding for challenging AIA patents based on prior art documents. It's faster and cheaper than litigation.
How it works:
- Petition filed with Patent Trial and Appeal Board (PTAB)
- PTAB decides whether to institute review (reasonable likelihood of success)
- If instituted, full adversarial proceeding between patent owner and petitioner
- Discovery is limited
- Decision typically within 12-18 months
4️⃣ Post-Grant Review (PGR)
Statute: 35 USC § 321
Availability: AIA patents ONLY (filed on/after March 16, 2013)
Timing: Within 9 months of grant
Who can request: Anyone (except the patent owner)
Grounds: ANY ground under § 101, 102, 103, or 112
⏰ SHORT WINDOW: PGR is only available for 9 months after the patent is granted. After that, you must use IPR (for documentary prior art) or ex parte reexam.
🎯 BROADEST GROUNDS: PGR is the ONLY post-grant proceeding that allows challenges based on:
- § 101 (subject matter eligibility, utility)
- § 112 (written description, enablement, indefiniteness)
- § 102/103 with ANY type of prior art (not just documents)
How it works:
- Similar to IPR but broader grounds
- Can use public use, on-sale, and other non-documentary prior art
- Can challenge on § 101 or § 112 grounds
- Conducted by PTAB
🧠 How to Choose on the Patent Bar Exam
Step 1: Check the Patent's Filing Date
- Filed before March 16, 2013? → Pre-AIA patent
- Options: Ex parte reexam OR Inter partes reexam
- Filed on/after March 16, 2013? → AIA patent
- Options: Ex parte reexam, IPR, or PGR
Step 2: Check the Timing
- Within 9 months of grant? → PGR is available (if AIA patent)
- After 9 months? → PGR window closed, use IPR or ex parte reexam
Step 3: Check the Type of Prior Art
- Patent or printed publication? → Ex parte reexam, IPR, or PGR all work
- Public use, on-sale, or other non-documentary? → ONLY PGR (and only within 9 months)
Step 4: Check the Ground of Challenge
- § 101 or § 112 challenge? → ONLY PGR (within 9 months of grant)
- § 102/103 with documentary prior art? → Ex parte reexam or IPR
📝 Common Exam Scenarios
Scenario 1: Patent filed April 1, 2013 (AIA). Prior art = printed publication. Challenge more than 9 months after grant.
Answer: IPR (C) or Ex parte reexam (A). IPR is more common/preferred for AIA patents.
Scenario 2: Patent filed February 1, 2012 (pre-AIA). Prior art = printed publication.
Answer: Ex parte reexam (A) or Inter partes reexam (B).
Scenario 3: Patent filed June 1, 2014 (AIA). Granted January 1, 2025. Today is May 1, 2025 (4 months after grant). Prior art = public use.
Answer: PGR (D) - only proceeding that accepts non-documentary prior art, and we're within 9-month window.
Scenario 4: Patent filed March 1, 2014 (AIA). Want to challenge on § 101 grounds (abstract idea).
Answer: PGR (D) if within 9 months. Otherwise, cannot challenge via post-grant proceeding (must litigate in court).
🎯 Quick Memory Aid
- Ex parte = "Ex" for "Everyone" (works for ALL patents, anytime)
- Inter partes reexam = "Old" system for pre-AIA patents (mostly obsolete)
- IPR = "I Pick References" (patents/publications only, after 9 months)
- PGR = "Pretty Great Range" (any ground, but only 9-month window)
