2. Strategies for Invalidation: How Are Patents Challenged?
Given the legal frameworks above, those seeking to invalidate a patent (be it a defendant in a lawsuit, a competitor, or a public interest group) often employ a combination of strategies:
2.1 Prior Art Search and Analysis
The cornerstone of most invalidation efforts is a thorough prior art search. The goal is to find publications, patents, or products from before the patent’s filing that read on the claims. As one guide succinctly put it, “the primary goal of patent invalidation is to locate any prior art the USPTO examiner might have missed”.
- Armed with strong prior art, a challenger can argue lack of novelty or obviousness. This might involve not just well-known literature but also obscure manuals, university theses, or even old products (catalogs, Wayback Machine archives of websites for on-sale evidence).
- In 2025, AI-driven search tools are increasingly used to uncover prior art including foreign language documents and even images (for instance, using image recognition to find similar diagrams that could invalidate a patent on a mechanical design).
- A notable strategy is the crowd sourcing of prior art – platforms where interested communities or experts are invited to find prior art (the Linux Foundation and EFF have done this to bust patents they consider problematic).
2.2 Choosing the Forum
A challenger must decide whether to attack the patent in court or via a patent office proceeding (or both). Often, if sued for infringement in the U.S., a defendant will file an IPR petition at the PTAB as a parallel strategy, hoping the PTO will cancel the claims or at least put pressure on the patent owner.
- If timing is an issue (e.g., you’re close to trial and Fintiv might block your IPR), you might stick to court. In Europe, one might file an EPO opposition if within the window, or use the UPC now for a broad revocation action.
- The choice may depend on perceived advantages: the PTAB has technical judges and no jury, which can be good for complex patents, whereas a jury trial in court might be riskier for a challenger but allows arguments like inequitable conduct that PTAB would not consider.
- Increasingly, challengers pursue multi-front attacks – for example, file an IPR to cover patentability issues and simultaneously argue other grounds (like lack of enablement or indefiniteness) in the court case.
2.3 Procedural Moves and Stays
When a post-grant review is instituted, challengers often move to stay the litigation, pausing the court case until the PTAB outcome. Courts in the U.S. frequently grant stays to conserve resources, especially if the PTAB is likely to simplify issues by invalidating some or all claims.
- This can benefit challengers by delaying any potential injunction or damages and possibly mooting the case entirely if the patent dies.
- On the flip side, patent owners sometimes try to avoid IPR by suing in venues or under timing that complicates the challenger’s ability to file (one tactic patent owners used was filing in the Eastern District of Texas and pushing a fast trial date to trigger Fintiv denials of IPR – although recent USPTO guidance has curtailed some of that).
2.4 Collaboration and Joint Defense
In cases where a patent is being asserted against multiple parties (like a so-called patent troll suing many tech companies on the same patent), those defendants often form a Joint Defense Group (JDG) to pool resources.
They might share the cost of prior art searches and jointly fund an IPR petition via one proxy filer. There are also third-party organizations like Unified Patents and RPX that specialize in filing IPRs to challenge patents that they see affecting their member companies.
Even outside defensive coalitions, we have seen non-profits join the fray: EFF famously crowdfunded and filed an IPR that successfully invalidated a broad podcasting patent which was used to sue podcasters.
This case is a great example of a public interest-driven strategy: the goal was not to defend a specific defendant but to eliminate a patent that threatened an entire community of content creators. The PTAB’s processes allow such public challenges, and 2025 may see more activism in this area (for example, challenges to patents viewed as hindering access to COVID-related medical technology, etc.).
2.5 Expert Testimony and Trials
In court litigation, invalidation often comes down to a battle of experts, especially on questions of obviousness or whether a technical disclosure is enabling.
A challenger will bring in expert witnesses to explain how prior art renders the patent obvious, or how a person of skill would find the patent’s teaching insufficient.
In complex fields like pharmaceuticals, an expert’s testimony that a certain experiment would require undue effort can be decisive (as essentially happened in Amgen v. Sanofi).
Conversely, patent owners use experts to argue the art was not so straightforward. By 2025, given the number of precedents, expert reports also heavily engage with what past cases have held – effectively, experts discuss KSR guidelines, Wands factors (for enablement), etc., to frame their opinions in legally meaningful ways. This fusion of legal precedent and technical testimony is a hallmark of modern patent trials on validity.
2.6 Appeals and Persistence
Even if a challenger loses initially (say a patent is upheld in an IPR or at trial), the fight may not be over. Appeals to the Federal Circuit can and do overturn patent validity findings. The appellate court might find a patent should have been invalidated and reverse a lower court (or vice versa).
Some famous patents survived initial challenges only to be invalidated years later on appeal or in subsequent cases. Thus, a comprehensive invalidation strategy plans for the long game, including possible re-challenges. Notably, if one challenger fails, sometimes another challenger can try again (with different art or arguments), unless estoppel applies.
For instance, if an IPR is not instituted, other parties might still get a shot in their own petitions.
