Identifying Grounds for Patent Invalidity: 5 Prior Art Pitfalls

Of the many reasons why someone might wish to invalidate a patent or patent claim, the two most common include preventative action from a competitor, and post-grant opposition and appeal to revoke a granted patent — such as in the case of infringement. In order to constitute grounds for patent invalidity, the affected parties frequently employ a patent invalidity or validity search.

On the surface, proving a patent’s invalidity may seem fairly straightforward. However, there are many complexities and perils in the process that could make or break a claim. Keep reading to learn the five most frequent pitfalls in prior art and how to avoid them.

Please note that though the details of this article are with respect to US patent law, the discussion points can be easily extrapolated for other jurisdictions.

How Do You Prove Patent Invalidity?

Broadly speaking, patent invalidity searches assess the strength of a granted patent, which we will refer to here as the “target patent.” In order to conduct this assessment, patent analysts must locate and evaluate relevant prior art (i.e. publications before a critical date that may pertain to a patent’s claim of being novel and nonobvious) that could have been used during prosecution to reject a patent application. 

The prior art uncovered during the search is then analyzed with respect to one or more of the target patent’s claims. An official patent invalidity search report will detail the mapping of each relevant piece of prior art to the individual claims of the target patent.

After locating relevant prior art, it can then be used to determine potential grounds for invalidity during litigation or post-grant proceedings, such as:

  • Inter-partes reviews (IPR)
  • USPTO opposition proceedings, such as post-grant review 
  • Assertions in an infringement suit
  • Assessments of patent portfolios for licensing or sale

Because of this range of extremely specific situations that may call for ascertaining the target patent’s grounds for invalidity, it is important to define the depth and scope of the search effort. 

Summary: Relevant prior art could potentially span multi-language publications from anywhere in the world and might involve a level of complexity regarding application, online publication, and print publication dates. For these reasons alone, it is important to build a comprehensive strategy for performing effective patent invalidity searches.

Pitfall #1 — Over Reliance On 102(b) Prior Art

Under US Patent law, 102(b) prior art is often considered the holy grail for anyone seeking to challenge a patent’s validity because it covers exceptions to the 102(a) provision that a person is entitled to a patent unless:

  1. The claimed invention was patented, in public use, on sale, described in a printed publication, or otherwise available to the public before the effective filing date of the claimed invention OR
  2. The claimed invention was described in a patent issued under section 151 [Citing the issue of an entitled patent upon payment of associated fees] OR in a patent/patent application which names another inventor and was effectively filed before the effective filing date of the claimed invention.

The superhero-like status of 102(b) prior art is due to its ability to anticipate the entire patent claim by:

  1. Citing disclosures published more than one year before the effective filing date of the claimed invention that were either:
    • a. Made by the inventor, joint inventor, or another individual who obtained the subject matter directly or indirectly OR
    • b. Publicly disclosed by inventor, joint inventor, or another individual who obtained the subject matter directly or indirectly.
  2. Citing disclosures appearing in patents/patent applications wherein:
    • a. The subject matter disclosed was obtained directly or indirectly from the inventor or joint inventor.
    • b. Previous to filing, the subject matter had been disclosed by the inventor, joint inventor, or another individual who obtained the subject matter directly or indirectly OR
    • c. The subject matter disclosed, and the claimed invention were owned or assigned to the same person (before the effective filing date).

While 102(b) prior art references are preferred due to simultaneously having been published before the target patent’s effective filing date and showing lack of novelty by disclosing all of the claim limitations, they can also be one of the most difficult types of references to identify.

For this reason, it’s important to broaden your search to include additional legal provisions that may disclose claim limitations through a narrower interpretation. Some examples include identifying a lack of novelty reference published, filed, or claiming priority before the effective filing date, or combining two or more prior art publications that show that the claimed invention is obvious or lacks an inventive step.

Summary: Limiting your search to 102(b) prior art can weaken your ability to challenge patent validity on several grounds. By preparing an array of prior art references that read on the claims, either individually or in combination, you increase your likelihood of providing relevant art to support a firm argument that can challenge the patent’s validity.   

Pitfall #2 — Blind Trust In Database Filters

Generally speaking, publications count as prior art if they have been published, filed, or claim priority before the target patent’s critical date. While the specifics depend on the type of publication and the jurisdiction of the patent, it can be intuitive enough to employ patent database system filters to restrict the search results by a variety of date fields, including but not limited to:

  • Publication Date / Issue Date
  • Application Date
  • Priority Filing Date (PRAD)

By using these filters, you can easily exclude publications that clearly would not qualify as prior art. One might assume that this date filtering function is useful — even foolproof — and that the date-filtered results must all count as prior art. This assumption is false.

Of course, best practice dictates that even these date-filtered results are thoroughly reviewed, and the relevant dates are confirmed. However, due to document codes and the innate structure of patent families, “phantom” patent applications will often appear in a patent family without an associated published document.

It’s almost a rite of passage to get your hopes up after catching a glimpse of a seemingly perfect reference in a patent family, only to find that the actual publications cannot be viewed. These “publications” are phantoms because they only serve to note that an application has been filed, though the actual contents of the application are not yet published. In short, always open the PDF publication file to ensure that it actually exists.

US patent publications must have their chain of priority claims checked via the PDF copy as this is the clearest way to determine whether new subject matter may have been introduced through continuation-in-part (CIP), via provisional patent application priority claims, or if a PCT application can be treated as a US patent filing alongside simultaneous international filings.

Ensemble IP Pro Tip: Bookmark the MPEP 102(e) Flowchart

The publication dates for non-patent literature (NPL) are more complicated than they appear because these same publications frequently appear online prior to print publication or are even mailed to subscribers before the official date of publication. Take note of the NPL publication record’s “available online date” or “date of mailing.”

Summary: As you can see, locating publications that qualify as prior art based on the critical date can be a bit more complicated than simply pulling the results after setting a database date filter. There is nothing worse than spending hours on a search and sending that “perfect” reference for attorney review, just to have it thrown out because the date was incorrect. Always verify and confirm!

Pitfall #3 — Drawing A Line At The Critical Date

Patent invalidity projects have clear calendar date boundaries that restrict what qualifies as prior art. However, another all too common pitfall is to automatically exclude all references published after the critical date.  The critical date should always be determined in consultation with the individual requesting the search, as it is not always the earliest priority date of the target patent.  

While at first glance it may seem counter-intuitive, best practice says that we should limit our search to one year after the critical date. Even though these publications don’t pass the critical date test to be considered prior art for the target invention, they can provide a wealth of information to an experienced searcher.

Innovation occurs in waves. These waves are accelerated and amplified by global stressors, such as the recent COVID-19 pandemic, leading to a mass of inventors and organizations innovating in the same space simultaneously. The output of this is a bevy of publications that tend to appear near the critical date that attempt to solve the same problem or to disclose the same technology as the target patent.

Though these newer publications cannot be used directly as prior art, they can be data-mined to extract relevant information about patent and non-patent literature publications via the citations, prolific inventors, innovative assignees, or terminology that describes the technology area or the specifics of the target invention.

Summary: By including publications that exist after the critical date, a patent searcher can more easily find relevant prior art that exists before the critical date. These newer publications have the potential to demonstrate how the technology may have evolved around or after the time of the target invention. Additionally, the inventors themselves could serve as invaluable expert witnesses during litigation. 

Pitfall #4 — Staunch “Broadest Reasonable Interpretation” Standard

Current and former patent examiners alike tend to stick to the “broadest reasonable interpretation” evaluation standard. This concept of broadly interpreting the claims is frequently inherited by patent search professionals as they learn the ropes of patent searching.

This mentality is so firmly ingrained in searchers’ heads that the standard approach is to consider the target claim in the most literal sense as written when searching for the patent grounds for invalidity. This tendency is further exacerbated by the typical format in which a patent invalidity search is requested: 

“Please invalidate this patent, with a focus on these specific claims.”

However, there is frequently no further discussion or insight provided, leaving the searcher to determine the interpretation of the claim.

In patent litigation, the claims should be viewed in light of the examination process, including but not limited to:

  • The examiner’s interpretation
  • The applicant’s arguments
  • The reasons for allowance
  • The Markman decision claim construction

Additionally, the team commissioning the patent invalidity search may have specific interpretations that they need to have considered during the search.

Summary: The most effective and efficient way of ensuring proper interpretation of the target patent’s claims is to discuss the interpretation framework as a part of the search consultation. Consider discussing whether the reasons for allowance are worth challenging and asking the commissioner to describe what their ideal reference would disclose. The answers to these questions will aid in narrowing the scope of the claims in question and arm the patent searcher with a clearer focus when evaluating potential prior art.

Pitfall #5 — Solely Focusing On Patent Literature

Due to the ease of searching patent data, it is often the first and last step in an invalidity search. It is true that patent data is very well-structured and global in scope. Additionally, the availability of English-language machine translations can make patent data the easiest source to search. Unfortunately, the ability to relatively quickly and easily perform a patent data search (especially in a time crunch) can often lead to missing relevant prior art.

By expanding your patent sources to include non-patent literature (NPL), you provide yourself access to prior art that discloses ideas that may not be within the patent domain or that exist prior to patent filings. Excellent NPL sources might include:

  • Journal articles
  • Product releases
  • Technology standards
  • Conference proceedings
  • Theses & dissertations
  • Textbooks
  • Product manuals
  • Videos
  • Blog posts

It is important to remember that not all inventors participate within the patent system, frequently because they are either unaware of patents or because they do not feel that a patent would be useful to themselves or their business. However, these same inventors will often publish their research or ideas for recognition in their field.

Non-patent literature publications have the potential to open new grounds for challenging the target patent, some of which are jurisdiction-specific, by proving that the target invention was previously made or sold using a common knowledge base for an obvious argument.

Summary: The most important consideration when utilizing non-patent literature is determining which types of publications are most likely to provide relevant results. Product manuals, public comments on technology standards, and even YouTube presentation videos are examples of non-traditional NPL sources that might disclose relevant prior art. Lastly, many publications are not digitized and are only available in print form — meaning that it is critical to access physical libraries and archives for these deep NPL searches.

Final Thoughts

Locating prior art that can be used to invalidate a granted patent requires an extensive search set up with the right scope and framework. Sticking to a broad interpretation of claims or limiting your search to 102(b) references could lead to missing out on valuable and relevant prior art with which to challenge the target patent. 

Consider implementing the learnings of this blog when mapping out your next patent invalidity search to ensure that you’ve provided the most thorough and comprehensive search results possible. Visit the Ensemble IP blog to read about the 5 Frequent Pitfalls of Freedom To Operate Analyses.

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