Patent Invalidity Explained: What Innovators and Legal Professionals Should Know

A valid patent can mean the difference between leading a market and losing ground to competitors. As one of the most powerful tools for protecting innovation, it gives the owner a clear advantage — but only if the patent meets strict legal standards.

That’s where patent invalidation comes in. Businesses, inventors, and third-party entities can challenge the enforceability of a patent through legal mechanisms — whether to defend against infringement claims, clear the way for new product launches, or reduce risk in licensing and acquisitions.

In this guide, we’ll break down the criteria for acquiring a valid patent (patentability), the most common grounds for invalidation, and the strategic reasons why legal teams and business leaders need to understand both. Whether you’re protecting your own intellectual property (IP) or assessing the strength of someone else’s, a firm grasp of patent invalidity is essential to any modern IP strategy.

What makes a patent valid? 

Generally, an issued patent is presumed valid because it has undergone extensive examination by the Patent Office within the U.S. Patent and Trademark Office (USPTO). As we’ll explore further below, this examination turns on the same factors parties raise in invalidity contentions and post-grant procedures. 

For a patent to be valid and enforceable, it must meet specific legal standards of patentability meant to ensure that only genuinely novel and useful inventions are protected. 

In this section, we’ll explore the five legal requirements for patentability and examine the role of the Patent Office in evaluating new patent applications.

The five legal requirements for patentability

To be considered patentable under U.S. patent law, the invention must satisfy five core requirements:

1. Patentable subject matter: The invention must fall within a category eligible for patent protection, such as a process, machine, article of manufacture, or composition of matter. Abstract ideas, natural phenomena, and laws of nature typically do not qualify.
   
   
2. Novelty: The invention must be new. It cannot have been publicly disclosed, sold, or patented anywhere in the world before the patent application’s filing date.
   
   
3. Non-obviousness: The invention must not be an obvious improvement or combination of existing knowledge to someone skilled in the field.
   
   
4. Utility: The invention must serve a practical purpose and be operable. It must do what it claims to do.
   
   
5. Enablement: The patent specification (or disclosure) must include a clear and complete written description that both demonstrates that the applicant had possession of the invention and enables others in the field to replicate the invention. This includes disclosing the best mode of carrying out the invention, as known at the time of filing.

Meeting all five criteria is essential for a patent to stand up to scrutiny during enforcement or in response to legal challenges.

Learn how DISCO helps firms navigate prior art review, prepare experts, and ensure defensibility in large patent cases.

Role of the USPTO in patent examination

The Patent Office within the USPTO is responsible for reviewing patent applications to determine whether they meet the criteria for patentability. The application process – also known as patent prosecution – involves examiners who evaluate the subject matter, novelty, non-obviousness, utility, and enablement of the claimed invention based on the content of the application and any prior art  available during the review. On average, the patent application process takes roughly two years, and can involve multiple requests for further information (also known as office actions) or amendments before the patent can be granted. 

However, the USPTO's patent examination process is not infallible — mistakes happen, and some patents are granted despite underlying validity issues. That’s why post-grant challenges and litigation play an important role in maintaining the integrity of the system.

Prior art

Prior art review is a significant part of the USPTO examiner's job.

Prior art refers to any evidence that the invention already existed or was known before the patent applicant filed their patent. It doesn’t have to be an identical product or invention — it just needs to describe or demonstrate the same idea or parts of it.

Prior art can include:

• Existing patents (even expired ones)
• Patent applications (filed before the one in question)
• Scientific publications
• Products sold or in public use
• Conference presentations, blog posts, websites, or any public disclosure that predates the filing

Example: The Sum of Known Parts

Say you’re trying to patent a smart coffee mug that:

1. Maintains temperature via a heating element
2. Syncs with your phone via Bluetooth
3. Sends an alert if it detects the mug is tipped over

If:

• Prior Art A discloses mugs with heating elements,
• Prior Art B describes Bluetooth-enabled drinkware,
• Prior Art C talks about spill sensors in baby bottles...

…then individually, none of these destroy the patent’s novelty. But a patent examiner (or a challenger) might argue that it’s obvious to combine these ideas, making your invention non-patentable due to lack of inventive step.

Key insight: A patent can be invalidated if a single prior art reference fully discloses the invention (anticipation) or if multiple references, when combined, make the invention obvious (obviousness). If all elements of your claimed invention appear across multiple pieces of prior art, it likely fails the non-obviousness test. If one document already covers everything, it fails the novelty test.

Why patents are challenged: common grounds for patent invalidity

Patents are powerful tools that provide exclusive rights to inventors — but they’re not airtight. Currently, 71% of challenged claims are found invalid.

Beyond legal requirements, there are also strategic motivations. Sometimes a company wants to bring a new feature to market but finds a competitor holds a blocking patent. Other times, non-practicing entities (NPEs) acquire patents simply to assert them against big tech players. Invalidation becomes a way to eliminate legal obstacles or defend against infringement claims.

Here, we explore the legal grounds for patent invalidity, and later, we’ll examine the strategic motivations in more detail.

Obviousness to a skilled practitioner

A patent can be invalidated if the invention is deemed "obvious" to a person having ordinary skill in the art (often abbreviated as PHOSITA). This means that even if the invention wasn’t explicitly disclosed in a single piece of prior art, it could still be invalidated if it would have been an obvious combination or modification of existing ideas.

The idea here is that patents are meant to reward true innovation, not trivial tweaks. If the average practitioner in a particular field — say, a mechanical engineer or a software developer — could reasonably have come up with the same invention by combining known elements, the patent may not be valid.

Example: Imagine a patent that covers a smartphone case with a built-in stylus holder. If stylus holders and smartphone cases were both well known before the patent, and it would have been obvious to integrate them, that patent might not withstand a challenge based on obviousness.

Insufficient disclosure or enablement

A patent must clearly and fully describe the invention and how to use it. This is the enablement requirement. It must also include a written description that proves the inventor actually possessed the invention at the time of filing.

This requirement ensures that the patent provides enough information for someone skilled in the field to reproduce the invention without undue experimentation. If the description is vague, missing key details, or overly broad compared to what the inventor actually created, the patent can be invalidated.

Example: If a biotech company claims a patent for a new method of gene editing but doesn’t explain how the method actually works or omits necessary steps in the process, the patent could be invalidated for lack of enablement.

Inequitable conduct 

Inequitable conduct refers to dishonest behavior by the patent applicant during the application process — particularly when they intentionally withhold or misrepresent material information to the Patent Office.

If a patent applicant fails to disclose relevant prior art or submits misleading data in bad faith, the entire patent can be deemed unenforceable. This doctrine is grounded in the idea that patents are a public right and should be granted only when the applicant plays fair.

Example: Suppose an inventor knew about a journal article that described a very similar technology but chose not to disclose it in their application. If it’s later discovered that the omission was intentional and that the prior art was highly relevant, the patent could be invalidated due to inequitable conduct.

Double patenting

Double patenting occurs when an inventor tries to get more than one patent for the same invention or for claims that are not patentably distinct. The law prohibits extending the life of a patent through serial filings for essentially the same invention.

The purpose of the rule is to prevent unjustified extensions of patent rights, which could unfairly block others from entering the market. The courts distinguish between "statutory" double patenting (same invention) and "non-statutory" or "obviousness-type" double patenting (different claims but not meaningfully different in substance).

Example: If an inventor first patents a type of folding bicycle, then later files a second patent with slightly modified claims that are just minor variations on the original folding mechanism, the second patent may be invalidated for double patenting.

Who can challenge a patent and how

Anyone with a legitimate interest — whether a competitor, investor, or even a third party looking to clear market space — can challenge a patent's validity. Challenges can arise during litigation, through administrative proceedings, or via strategic actions outside the courtroom. Understanding how these challenges are made is essential for both defending a patent and preparing an effective strategy to invalidate one.

Below are the primary avenues for challenging patent validity, each with distinct rules, timelines, and strategic benefits.

Administrative proceedings at the PTAB

The Patent Trial and Appeal Board (the PTAB or the Board), a body within the USPTO, oversees two key administrative processes for challenging patents: Post-Grant Review (PGR) and Inter Partes Review (IPR).

• Post-Grant Review (PGR): Available within the first nine months after a patent is granted, PGR allows challengers to contest validity on any grounds — including lack of novelty, obviousness, insufficient disclosure, and even subject matter eligibility.
  
  
• Inter Partes Review (IPR): This process is available after the PGR window closes. It is strictly limited in scope to novelty and non-obviousness grounds based solely on prior art consisting of patents and printed publications.

Faster and often more cost-effective than federal court litigation, these patent invalidity processes are conducted by administrative judges who specialize in patent law and rely heavily on documentary evidence like prior art and expert declarations.

Strategic Considerations: Post-Grant Review and Inter Partes Review shift the burden of proof to the challenger, who must show the patent is more likely than not invalid. Many companies prefer PTAB proceedings because they're typically resolved within 12 to 18 months, which is significantly faster than federal litigation.

Example: A software company planning to launch a feature that resembles a competitor’s patent may file for IPR to challenge that patent’s novelty before proceeding with development.

Federal court litigation

In district court, a party accused of patent infringement can assert patent invalidity as a defense, triggering a full litigation process where the court evaluates the patent’s enforceability.

This is the traditional path for resolving patent disputes. Unlike PTAB proceedings, federal litigation allows a broader range of invalidity arguments, including inequitable conduct, and may involve a jury. The legal standard is also higher — “clear and convincing evidence” must be presented to invalidate a patent.

Before initiating a formal challenge, legal professionals typically begin with patent invalidity research and analysis. This includes reviewing prior art, analyzing the patent’s claims and specification, and identifying legal or procedural vulnerabilities as described above. A thorough patent invalidity analysis helps determine the likelihood of success in proceedings like IPR or federal litigation and informs key strategic decisions, from whether to challenge to how aggressively to proceed.

Courts often rely on technical experts to explain how an invention compares to prior art or industry standards. These experts play a crucial role in helping juries or judges understand whether the patent truly meets legal requirements.

Example: If a telecom company sues a rival for infringing on its call-routing patent, the defendant might respond by arguing the patent is invalid because the claimed invention was obvious based on older technology.

Other legal mechanisms

Patents may also be challenged anonymously or outside the courtroom. For example:

• Third-Party Submissions: Before a patent is granted, outside parties can submit prior art to the USPTO along with explanations of its relevance. This doesn’t invalidate a patent directly but can influence whether the application is approved.
  
• Ex Parte Reexamination: Anyone can request that the USPTO reexamine an issued patent based on prior art. If granted, the patent holder must defend the patent’s validity in a closed proceeding with no active participation from the challenger.
  
• Derivation Proceedings: If someone believes a patent applicant stole their idea, they can file a derivation claim at the PTAB to contest ownership.‍

These mechanisms can be part of a broader IP strategy — used to reduce litigation risk, signal a defensive posture, or slow a competitor’s progress.

Example: A startup might use third-party submission to alert the USPTO to prior art during a competitor’s application review, hoping to block issuance without launching a full legal battle.

Strategic reasons for challenging patent validity

Challenging a patent is often a calculated business strategy. Whether a party is defending itself against infringement claims, trying to clear a path for innovation, or evaluating a company for investment, questioning the validity of a patent can serve as a critical leverage point.

The U.S. patent system is designed to balance innovation with fair competition. When that balance tips — because a patent was issued in error, is too broad, or is weaponized — legal tools exist to restore it. Below are the most common strategic motivations behind patent challenges.

Defense use in infringement cases

When accused of patent infringement, one of the most powerful tools a defendant has is to assert invalidity as a defense, arguing that the patent should never have been granted in the first place. This procedure begins early in an infringement case with disclosures known as invalidity contentions, and continues through declaratory judgment, summary judgment, and trial.

If successful, the defendant doesn’t just avoid liability. They eliminate the threat entirely. The burden of proof shifts to the challenging party, who must show invalidity by clear and convincing evidence in court or meet a preponderance of evidence standard in proceedings before the PTAB. Common tactics include identifying prior art that shows the patent is obvious or arguing that the invention is not fully enabled.

Example: A small startup accused of infringing a patent may use prior art to invalidate the patent as part of its legal defense. If successful, it removes the threat of injunctions and damages.

Competitive and market strategies

Some companies challenge patents not because they’ve been sued, but because those patents stand in the way of their growth. Invalidating a competitor’s patent can clear the runway for launching a new product, entering a new market, or avoiding costly licensing deals.

In more aggressive scenarios, NPES (also known as patent assertion entities or PAEs) or may acquire patents solely to enforce or invalidate them for financial gain. Conversely, large tech companies with significant IP portfolios may seek to invalidate patents held by NPEs as a defense or deterrent against excessive litigation.

Example: A tech firm developing a video conferencing feature may identify a competitor's patent that could block its launch. If they believe the patent is overly broad or unsupported, they might initiate a PTAB challenge to invalidate it and move forward with confidence.

IP portfolio and transactional due diligence

Patent validity plays a major role in valuing intellectual property during mergers, acquisitions, or licensing negotiations. A portfolio that includes weak or invalid patents poses a risk to buyers, investors, and partners — especially if those patents are central to the company’s valuation or market position.

Due diligence teams often scrutinize patents for strength, enforceability, and prior art risk. If red flags arise, the buyer may demand indemnities, adjust pricing, or walk away from the deal. On the flip side, sellers may proactively seek validity opinions or conduct internal audits to identify and correct weaknesses before going to market.

Example: During acquisition talks, a medical device startup’s flagship patent is flagged as potentially invalid due to a lack of novelty. The acquiring company reduces their offer, citing the legal risk associated with enforcing the patent.

How to protect a patent from invalidation

Patent challenges are a reality of the innovation landscape, but patent holders can take proactive steps to reduce the risk of invalidation. A strong IP strategy begins well before litigation ever enters the picture. 

The first step is to engage a patent lawyer, or have a patent lawyer draft and prosecute your patent. Below, we'll explore some best practices used by legal teams and inventors to defend their patents from future attacks.

Strong and balanced claim drafting

Drafting claims is both an art and a science. Claims must be precise enough to define the boundaries of the invention without being so broad that they cover prior art or obvious variations. Overly narrow claims may limit enforceability, while overly broad ones invite validity challenges. A balanced approach ensures clarity, defensibility, and appropriate scope within the technical field.

Tips to execute:

• Avoid overbroad language that could encompass prior art or generic implementations. Be specific in what the invention is and is not.
  
• Use dependent claims to layer in variations, fallback positions, or use cases that narrow scope while preserving flexibility.
  
• Benchmark claims against competitor patents to ensure your invention is clearly differentiated.
  
• Have a technical expert review the claims for clarity and consistency with the invention’s actual implementation.
  
• Consult a patent lawyer early to ensure your claims are not only grantable but defensible, and that the claims do not do not employ language that inadvertently limits their scope.

Detailed and enabling specification

A patent specification should do more than describe the invention — it must teach someone skilled in the art how to make and use it without undue experimentation. Including clear implementation details, diagrams, and real-world examples helps satisfy the enablement requirement. This level of specificity provides evidentiary strength if validity is later questioned.

Tips to execute:

• Include real-world use cases, flowcharts, or diagrams to visually and functionally describe how the invention works.
  
• Use multiple embodiments or variations to demonstrate flexibility and thoroughness.
  
• Avoid vague terminology — define key terms with precision in a dedicated “Definitions” section.
  
• Describe potential implementation challenges and how to overcome them, showing enablement without undue experimentation.
  
• Have a peer or technical reviewer attempt to understand and replicate the invention using only the spec to test completeness.

Consistency between claims and description

Discrepancies between the claims and the body of the patent can raise red flags. For example, if the claims introduce terminology not supported or defined in the specification, a court may find the patent lacks adequate written description. Maintaining alignment in scope, terminology, and definitions throughout the document reduces the risk of ambiguity-based invalidation arguments.

Tips to execute:

• Ensure each claim term is explicitly supported in the specification.
  
• Align terminology across the entire patent — don’t use synonyms or unintroduced phrasing in claims.
  
• Review claims and specification side-by-side before submission to catch scope mismatches.
  
• Use the same logic and sequencing in both sections to avoid confusion.
  
• Update the specification when amending claims during prosecution to maintain alignment.

Comprehensive prior art search

Failing to uncover relevant prior art before filing is one of the most common pitfalls in patent prosecution. Conducting an exhaustive prior art search — including international patents, publications, product manuals, and even conference proceedings — helps draft stronger claims and avoid novelty or obviousness issues. A good search isn’t just a checkbox; it’s a foundation for defensibility.

Tips to execute:

• Search across multiple databases, including USPTO, EPO, WIPO, and commercial platforms.
  
• Expand search terms to include synonyms, related functions, and adjacent technologies.
  
• Include non-patent literature like white papers, manuals, product brochures, and academic research.
  
• Perform a cited-reference search on similar patents to trace back foundational ideas.
  
• Document your search thoroughly to support later patentability or litigation decisions.

Competitive landscape monitoring

Even after a patent is granted, threats can emerge as new filings appear. Monitoring competitors’ patent activity helps you spot potential overlapping claims, anticipate infringement risks, and identify opportunities to narrow or amend claims in follow-on applications. This vigilance also informs defensive publishing strategies that prevent others from patenting similar innovations.

Tips to execute:

• Set up alerts in patent databases (e.g., USPTO PAIR, Google Patents) for key competitors and tech areas.
  
• Track continuation filings from major players — they may signal strategic directions or future blocking patents.
  
• Use analytics tools (like PatentSight, LexisNexis, or PatSnap) to identify portfolio growth patterns or litigation activity.
  
• Perform quarterly IP reviews to update your team on changes in the competitive IP environment.
  
• Evaluate new filings for overlaps or emerging infringement risks and respond accordingly.

Use of continuous and divisional applications

Strategically filing continuation, continuation-in-part (CIP), or divisional applications allows patent holders to protect different embodiments or aspects of an invention over time. These tools can be used to hedge against invalidity claims by preserving broader or narrower claim scopes, or by adapting to evolving competitive and technological contexts.

Tips to execute:

• Develop a long-term filing strategy that maps out follow-ons for each key innovation.
  
• Use continuations to adapt claims to evolving industry trends or competitive pressures.
  
• File divisionals when multiple inventions are disclosed in one application to maintain protection over time.
  
• Stagger application timing to keep flexibility in how and when you assert IP rights.
  
• Preserve optionality by not claiming everything at once — use continuation strategy to build layered IP protection.

Regular IP portfolio audits

Patents shouldn’t gather dust. Periodic reviews of your portfolio help identify weak spots, ensure claims are still aligned with business goals, and assess litigation readiness. Audits can also uncover patents that are no longer commercially useful — allowing businesses to trim costs, reallocate resources, or repurpose filings for cross-licensing opportunities.

Tips to execute:

• Create an IP audit checklist covering claim scope, enforceability, commercial alignment, and citation strength.
  
• Review granted patents annually for relevance to current products and business goals.
  
• Retire or abandon patents that are no longer strategically useful to reduce maintenance fees.
  
• Use audit findings to identify licensing or enforcement opportunities.
  
• Include litigation-readiness checks, such as reviewing chain of title, claim clarity, and known prior art exposure.

Validity opinions from independent counsel

When in doubt, bring in a fresh set of eyes. Independent legal opinions on a patent’s validity — based on thorough analysis of the claims, specification, and known prior art — can reveal vulnerabilities before opponents do. These evaluations are especially valuable before asserting a patent, entering a licensing agreement, or going into due diligence for a merger or acquisition.

Tips to execute:

• Engage external counsel with technical and litigation experience.
• Request both an initial “red flag” review and a more in-depth validity opinion if concerns arise.
  
• Use opinion letters proactively before asserting the patent, raising funds, or entering M&A discussions.
  
• Ask counsel to test the patent under real-world invalidity arguments (e.g., obviousness, lack of enablement).
  
• Maintain documentation securely, as opinions may become material in litigation or due diligence contexts.

Implications of invalidation for businesses and investors

Patent invalidation can create ripples across an entire business. For innovators, investors, and potential buyers, the enforceability of a patent is often directly tied to a company’s market position and perceived value. 

Whether as part of an IP licensing model, product exclusivity, or an M&A negotiation, a strong patent strengthens leverage. When that protection is lost or put in doubt, strategic plans can be delayed, devalued, or even dismantled.

Below, we explore the business and financial consequences of patent invalidation, along with practical steps organizations can take to manage risk.

Strategic and financial consequences  

When a patent is invalidated, it removes a barrier to entry — allowing competitors to develop, market, or sell similar products without fear of infringement. This can erode exclusivity, undermine pricing power, and collapse a once-protected revenue stream.

For companies that monetize their patents through licensing agreements, invalidation can trigger renegotiations, refunds, or termination clauses, especially when the license was based on exclusive rights. Invalidation can also weaken leverage in lawsuits, often turning a would-be plaintiff into a vulnerable defendant in countersuits.

For investors, the impact can be equally serious. IP portfolios often form a significant portion of a company’s valuation, especially in tech, biotech, and manufacturing. When a cornerstone patent falls, it may cause a ripple effect in investor confidence, stock price, and deal viability — particularly in late-stage funding or pre-acquisition due diligence.

Risk mitigation and preparedness  

To reduce the strategic and financial fallout of a potential invalidation, businesses should adopt a proactive IP risk strategy. This includes:

• Maintaining detailed invention records, including lab notebooks, early drafts, and communications that demonstrate development and originality.
  
• Conducting internal audits to assess the strength and relevance of each patent, and flag those most vulnerable to challenge.
  
• Evaluating insurance products, such as IP defense policies or patent infringement liability coverage, that can offset litigation costs and financial exposure.
  
• Creating contingency plans for critical patents, including defensive publishing or fallback product designs.
  
• Consulting litigation counsel early when a high-value patent may become the target of a challenge, ensuring preparedness with expert declarations and prior art research.

By anticipating and planning for potential validity challenges, businesses can safeguard not only their innovations but also the financial models and partnerships built around them.

Conclusion

Understanding patent validity and the many ways it can be challenged is essential for anyone navigating the intellectual property landscape. Whether you’re defending your own innovations or assessing the strength of a competitor’s claims, a working knowledge of invalidation grounds, strategic motivations, and protective best practices is key to making informed legal and business decisions. 

As patent law continues to evolve alongside technological advancement, innovators and legal professionals alike must adopt a proactive, informed approach to patent strategy — one that safeguards valuable IP while remaining prepared to navigate challenges with confidence and precision.

Need help with patent invalidity research? DISCO’s forensics team has a strong track record in protecting intellectual property.

‍Lean on DISCO’s deep expertise in patent litigation. Here how we can help navigate prior art review, prepare experts, and ensure defensibility in large patent cases.