Types of Prior Art Used in Patent Invalidity Searches : What can be used as a prior art

Types of Prior Art Used in Patent Invalidity Searches : What can be used as a prior art

Table of Contents

Introduction

A patent invalidity search is conducted to find prior art that can be used to challenge the validity of a granted patent. The term “prior art” refers to any publicly available information that existed before the filing date of the patent in question. If prior art proves that the invention was already known or obvious, the patent can be declared invalid in court or by a patent office.

Understanding the different types of prior art is crucial for anyone conducting patent invalidity searches—whether you are an attorney, a business defending against infringement claims, or an innovator ensuring that your patents are strong and enforceable.

This article provides a comprehensive breakdown of the various types of prior art used in patent invalidity searches, along with real-world case examples demonstrating how each type of prior art has played a key role in invalidating patents.

What is Prior Art?

Prior art includes any evidence that an invention was known to the public before the patent application filing date. It does not need to exist in the same country as the patent being challenged—it can come from anywhere in the world.

To invalidate a patent, prior art must show that the patented invention lacks novelty or is obvious based on earlier knowledge. The most common sources of prior art include:

  1. Patent Documents (Previously Granted Patents & Patent Applications)
  2. Scientific Literature & Technical Publications
  3. Books, Magazines, and Industry Journals
  4. Online Disclosures & Internet Publications
  5. Products on the Market (Commercial Prior Art)
  6. Public Use or Sale Before Filing (On-Sale Bar)
  7. Academic Theses, University Research & Conference Papers
  8. Government Reports, Standards, and Regulations

Let’s explore each type in detail, with real-life cases where they played a role in patent invalidation.

1. Patent Documents (Granted Patents & Patent Applications)

One of the most powerful forms of prior art is earlier patents or published patent applications. If an invention has already been patented, or if a previously filed patent describes the invention, the later patent is invalid due to anticipation (lack of novelty).

Case Study: Merck & Co. v. Teva Pharmaceuticals (2010)

Background: Merck had a patent for the osteoporosis drug Fosamax. Teva Pharmaceuticals challenged this patent by citing an earlier patent application that described a similar drug formulation.
Outcome: The court ruled that Merck’s patent was anticipated by earlier prior art, and the patent was invalidated.

Lesson: Patent documents are a primary source of prior art, and even unpublished applications can be used if they were eventually made public.

2. Scientific Literature & Technical Publications

Publications in scientific journals, technical reports, and research papers can serve as strong evidence of prior art. If an invention is described in peer-reviewed research, it can be used to challenge a patent’s validity.

Case Study: Ariad Pharmaceuticals v. Eli Lilly (2010)

Background: Ariad Pharmaceuticals sued Eli Lilly for infringing a gene-regulating drug patent. Eli Lilly cited earlier scientific publications that already described the core invention.
Outcome: The court ruled that Ariad’s patent was invalid because its invention was already disclosed in scientific literature before filing.

Lesson: Published scientific papers can serve as prior art and are often used in biotech and pharmaceutical patent disputes.

3. Books, Magazines, and Industry Journals

Printed materials such as textbooks, trade magazines, and industry journals can also be used as prior art. These sources often contain technical information and innovations that were publicly known before the patent filing date.

Case Study: Amazon’s “One-Click” Patent (2007)

Background: Amazon patented its “one-click” online purchasing system. Barnes & Noble challenged this patent by presenting prior publications in e-commerce journals that described similar concepts before Amazon’s patent was filed.
Outcome: The patent was partially invalidated, reducing Amazon’s exclusivity over the technology.

Lesson: Even non-technical books and magazines can serve as prior art if they contain a description of the invention.

4. Online Disclosures & Internet Publications

Information posted online—including websites, blogs, forum posts, and archived web pages—can be used as prior art if they were publicly accessible before the patent’s filing date.

Case Study: Wayback Machine Used as Prior Art Evidence

Courts have increasingly accepted internet archives (such as the Wayback Machine) to prove prior art. If a website contained the same invention before a patent was filed, it could be used to invalidate the patent.

Lesson: Internet archives and blog posts can be valuable sources of prior art and are now widely used in patent litigation.

5. Products on the Market (Commercial Prior Art)

A patent can be invalidated if the same product was already available in the market before the patent was filed. This includes products sold by competitors, prototypes, or even devices shown at trade fairs.

Case Study: Pfaff v. Wells Electronics (1998)

Background: Pfaff filed a patent for a computer chip socket but had already sold it six months before filing the patent application.
Outcome: The Supreme Court ruled that since the invention was commercially available before filing, the patent was invalid.

Lesson: If an invention was already being sold, it cannot be patented later.

6. Public Use or Sale Before Filing (On-Sale Bar)

If an invention was used publicly or sold before the patent filing date, the patent can be invalidated.

Example:

A company showcases a new smartphone feature at a public tech exhibition but forgets to file a patent. If a competitor patents it later, the public demo can be used as prior art to invalidate the patent.

Lesson: Public demonstrations and product sales count as prior art and can be used in invalidity searches.

7. Academic Theses, University Research & Conference Papers

University PhD theses, conference presentations, and dissertations can also serve as prior art if they were publicly available before a patent’s filing date.

Lesson: Academic research can be critical prior art, especially in high-tech and pharmaceutical patents.

8. Government Reports, Standards, and Regulations

Official government documents, technical standards, and regulations may also serve as prior art.

For example, FDA reports on a drug formulation can be used to challenge a pharmaceutical patent.

Lesson: Government reports can be highly credible prior art, especially in regulated industries.

Conclusion

A patent invalidity search requires examining all types of prior art to identify evidence that can challenge a patent’s validity. The key types of prior art include:

  • Patent documents
  • Scientific papers & journals
  • Books, magazines & industry journals
  • Online content & archived web pages
  • Commercial products & market releases
  • Public use or sale before filing
  • University theses & conference presentations
  • Government standards & reports

Conducting a thorough invalidity search can save businesses millions of dollars in legal risks and licensing costs. If you need a professional patent invalidity search, contact us today!

Why an Invalidity Search Is a High-ROI Investment

Patent Invalidity Search Report
Patent Invalidity Search Report

A well-executed invalidity search can mean the difference between:

✔ Winning vs. Losing a Patent Litigation – A single overlooked piece of prior art can make or break a case, saving millions in damages and legal fees.

✔ Gaining vs. Losing Negotiation Leverage – Invalidating a competitor’s patent before entering a licensing or infringement dispute can shift the power dynamics in your favor.

✔ Securing vs. Risking Market Freedom – Before launching a product, knowing whether an asserted patent is truly valid can prevent unnecessary licensing fees or redesign costs.

Simply put, an invalidity search is not an expense—it’s an investment with the potential for significant financial and strategic returns. However, we know that you may want to validate the quality of our work before committing to long-term projects.

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Prasad Karhad
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