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  • Gagandeep Singh

10 Prior Art Search Mistakes That Undermine Your Inter Partes Review

An Inter Partes Review (IPR) is a trial held before the USPTO’s Patent Trial and Appeal Board (PTAB) to cancel specific claims of a patent on a ground that could be raised under §102 or §103, and only on the basis of prior art consisting of patents or printed publications.


An IPR petition may be filed by any person who is not the patent owner and who has not filed a civil lawsuit challenging the validity of the patent. IPR proceedings are available 9 months after the grant date for patents issued under the AIA first-to-file rules, and for all patents filed before the first-to-file rule took effect. A petition for IPR must be filed within one year from the date of service of a patent infringement complaint.

Prior art search is the most important part of any IPR to invalidate a patent (subject patent). Below a list of top prior art search mistakes that can most often undermine IPR petitions and trials:

1. When the Novelty is Not Fully Understood

The wrong interpretation of the novelty of a subject patent leads to a wrong prior art search. The novelty of the subject patent can generally be understood by reading the patent or independent claim thoroughly. For complex patents, novelty can be better understood by going through Public Patent Application Information Retrieval (PAIR) document history. Public PAIR is an online service provided by the USPTO for general public to access information regarding patents and published applications. It allows users to see prosecution history of US patents and patent applications. Prosecution history describes the interaction between applicants of the subject patent and a patent office. Prosecution history describes the amendments made in the claims of the patent on the basis of the examiner’s objection and/or prior search results provided.

35 USC §102: “A person shall be entitled to a patent unless—
(1) the claimed invention was patented, described in a printed publication, or in public use, on sale, 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 , or in an application for patent published or deemed published under section 122(b) , in which the patent or application, as the case may be, names another inventor and was effectively filed before the effective filing date of the claimed invention.”

2. When a Wrong Priority Date is Picked.

Priority Date, Filing Date, Publication Date and Grant Date of a patent play different role in any prior art search.

The priority date is generally the earliest filing date of a subject patent or its family patents, i.e. it is generally the filing date of the earliest application that disclosed the subject patent’s specification. A patent’s life term is calculated based on its priority date. The filing date of a patent is the date on which the patent’s own application was filed. The publication date of a patent is the date on which the patent office made the application public and is usually 18 months after the filing date. The grant date of a patent is the date on which the patent was granted after examination by the patent office. A patent can be enforced in a patent infringement case only after it has been granted.

For non-patent literature (such as research papers, product manuals, etc.) and, in most cases, foreign patents to be considered as prior art for a subject patent, they must have been published before the priority date of the subject patent.

For US patents and applications to be considered as prior art for a subject US patent, they must have been filed before the priority date of the subject patent.

3. When the Prior Art Search Relies Only on the Claims of a Prior Art Patent.

It is a common misconception that a patent prior art can be used to invalidate a subject patent only if its claims map on the novelty of the subject patent. A prior art reference can disclose the subject patent’s invention anywhere in its description. The only condition is that its filing or publication date must be before the priority date of the subject patent.

4. When the Prior Art Search Misses NPL References

Prior art for a subject patent need not be restricted to patents or patent applications. Non-Patent Literature (NPL), which includes any type of literature such as research papers published in academic journals or presented in any conference, product user manuals, user guides and/or product application documents, and Non-Digitized NPL (includes offline literature such as magazines, newspapers, books, pictures, academic journals and/or user manual) must be included in a prior art search for it to be successful. If any of the NPL is missed, it can harm the IPR.

5. When Prior Art Search Misses Actual Products Available at the Time

A strong prior art can be found even in products (launched before the priority date of the subject patent) but which may have since been discontinued and for whom literature such as user guides and manuals may no longer be available. It is in fact sometimes easier to show the same technology in the physical product than in the documents, once the product is identified and procured. Such a prior art search is stronger if it can be substantiated by reverse engineering and/or source code analysis of the product, showing that the prior art product embodied each of the claim limitation before the priority date of the subject patent.

6. When Claim Terms Are Not Construed Correctly

Claim construction refers to the legal interpretation of claim terms. Generally, prior art searches would use claim terms used in the subject patent for making search strings while searching for a prior art. Search strings includes every possible synonym and combinations of the claim terms that might be used by a different inventor in their patent or NPL. Therefore it becomes important for searchers to know and consider the correct construction of the claim terms. Using a narrower construction than necessary may miss out on important prior art. But using a construction that is over-broad results in too many false positives and generally would increase costs of analysis later.

The correct construction to be considered for claim terms comes generally from the description and the prosecution history of the patent. For example, the claim term “multimedia” may include all text, audio, video or any other data, but if it restricted to the audio and video in the patent itself then text must be excluded from the search string.

Only in cases where neither the description nor the prosecution history sufficiently define a term, the searcher must rely on extrinsic sources such as industry dictionaries and manuals.

7. When the Combination of §103 Prior Art References Would Not Have Been Obvious.

While searching for a prior art, a combination of two patents, a patent and a patent application, or a patent and an NPL can be considered in combination in order to render a claimed invention obvious. Beyond the fact that the combination discloses each of the claim limitations, a person having ordinary skill in the art (PHOSITA) must have at the time of the invention found it obvious to combine the two references in order to arrive at the patented invention. For example, in a very broad sense, the combination can be said to be obvious if both the references are from same field; even better, if they both address the same problem. Combining two or more references that relate to different technology areas would have little chance of success in invalidating a subject patent.


35 USC §103: ‘’A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.’’

8. When Proper Prior Art Search Tools Are Not Used

A prior art search cannot rely on just Google and/or free search engines – because the search interface usually offers very limited functionality and their coverage only spans a few popular patent offices or journals. There are however many paid patent databases available for prior art search and NPL searches, such as Orbit Intelligence by Qestel, PatSnap, PatBase, etc. that provide the ability to form more complex search strings.

We at Copperpod, for example, use Orbit Intelligence for its wider coverage as well as its ability to perform complex searches (including use of wildcard expressions and operators) and generate useful analytics.

9. When Prior Art Search Results Were Already Cited By Or To The Examiner

For any prior art search, it is important to make an exclusion list before performing the search. An exclusion list should include all the patents and NPL cited by the subject patent and family patents of the subject patent, because in most cases it can be presumed that the examiner considered those references and found that the subject patent was novel in view of those references.

10. When the Right Experts Are Not Retained

An IPR petition would in most cases be accompanied with a report by a technical expert on whose testimony the petitioner intends to rely on at the trial. However, often the petitioner’s counsel relies on certain technical experts because they have worked with them before or are more comfortable working with them. However, even if they do not finally submit a report, it is advisable to consult academicians and industry experts who were working on the technology (described in the subject patent) around the same time when the subject patent was granted. At a minimum those experts can provide guidance for the searchers, counsel and the eventual testifying expert. Even more importantly, their institute archives (online or offline) or company documents (if not confidential) can be a great source of prior art.


In IPRs and patent litigation (and arguably in life as well), it takes a thousand correct steps to win, and only one incorrect step to lose. The mistakes listed above are by no means exhaustive, but are certainly the most common ones we have encountered while helping our clients not only file successful IPR petitions but also while helping our clients successfully defend their patents against IPRs.


Did you encounter any of these as well – or encounter new ones during your IPR campaign? Write to us at info@copperpodip.com.


#priorartsearch #intellectualproperty #ptab #invalidity #ipr

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