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IMS Expert Insights: An Expert Witness Perspective on Inter Partes Review of Patents



| By Dr. Michael S. Lebby, IMS Elite Expert

An inter partes review (or IPR) of a patent is a trial proceeding conducted by the Patent Trial and Appeal Board (PTAB) when there is a challenge to patentability. The procedure for conducting IPRs took effect in 2012 and applies to all patents, regardless of the date of issuance. It has streamlined the process and the cost of patent challenges by restricting the process to one year and limiting discovery.[i]

An IPR is commonly heard by a panel of three judges who typically have technical backgrounds. However, the judges may not be well-versed in the specific technology in question in the patent matter at hand, which means that expert witness testimony can significantly impact the outcome of an IPR proceeding.

It is important for attorneys who represent patent owners to seek out expert witnesses who quickly grasp a broader view of prosecution history and inventors’ motivations, in addition to the technology at issue. Further, counsel must assist the expert in these efforts to ensure their opinion stands up to scrutiny during cross examination.

Patent litigation cases can be won or lost through the actions and competency of an expert witness—making their role not only important but crucial. Below, we will take a close look at the part an expert witness plays during the inter partes review and consider how the IPR process could be improved.

IPR Process Overview

Over the past several years, IPR proceedings have changed considerably. A decade ago, the IPR process was reasonably independent from International Trade Commission (ITC) and District Court proceedings. Today, when an expert is brought in to evaluate a patent dispute, the first stage is often to “pressure test” the patent-in-suit by initiating an IPR.

Once the IPR process has been initiated, the task of the expert witness is to support the patent owner.[ii] An IPR typically focuses on the issued patent claims of an issued patent. The presumption is that claims are assumed to be issued correctly from the United States Patent and Trademark Office (USPTO).

Expert Witness Engagement

Before any patent litigation case, the first requirement is to review conflicts of interest. The key areas the expert witness needs to focus on are conflicts with the opposing client and/or opposing counsel. Expert witnesses often have deep technical experience in narrow, well-defined disciplines, which allows for some flexibility in the areas of conflicts.

Prosecution History

An expert witness must perform a thorough review of the prosecution history[iii] before crafting a declaration. The prosecution history of a patent(s)-in-suit conveys what the inventors argued before the USPTO. Even though the files for the prosecution history can be more than one thousand pages in length, the key facts are often found in the examiner’s office action and counsel’s responses.[iv]

Summary of Background & Qualifications

An expert witness should demonstrate that at the time of the invention, they were qualified to be at least a person of ordinary skill in the art.[v] An effective way to do this is to give an overview of the expert’s curriculum vitae. It helps to focus on those competencies that relate to the case at hand. Examples of previous publications that include patents are useful for demonstrating skills and knowledge. This section can be very short in word length at times, and typically is used in multiple reports. However, the first or initial report or declaration should at least provide a broad overview of the technical skills to support the expert witness’ opinions in the declaration.

Materials Reviewed

The IPR report or declaration must contain a section that details which materials, documents, books, papers, patents, etc. were reviewed in the process of generating an expert opinion.[vi] Experts sometimes get into trouble if they have not read or reviewed everything on the list, or if they exclude extrinsic materials. Even simple website searches should be included, but often are not.

Relevant Legal Standards

This is the one section of a declaration, expert report, or similar document that the expert witness typically does not write themselves; they tend to leave it to counsel. In general, this section should notify opposing counsel that the expert witness is not an attorney and that the expert witness will understand the applied legal standards to generate expert opinions. Common sections of relevant legal standards for IPR processes[vii] include for example, anticipated versus obvious patent claim analysis, the doctrine of equivalents[viii] (or DOE), and the enablement requirement.[ix] While the expert witness does not have to memorize the legal code or language, they will be expected to apply the code or language to support their opinions.

Level of Ordinary Skill in the Art

This section of the IPR process is sometimes overlooked and may be contested aggressively. There are IPR cases where the level of ordinary skill in the art is well-aligned with the patent owner, and the subject is never discussed. However, this author has observed IPR cases in which whole depositions have been dedicated to this section.

The qualifications of a “person of ordinary skill in the art” (POSITA) can be important for an IPR declaration, and the selection of a POSITA should be carefully written by the expert witness. A key component is to define the formal and informal education and relevant experience of a POSITA at the time of the invention. One measure that can be used is hypothetical: what would you look for in terms of skill set and experience if you were to hire someone at the time of the invention to undertake a similar task to the patent(s)-in-suit in your commercial organization? While the answer is not definitive, it does provoke thought as to the definition of a POSITA.

Summary of Opinions

An expert witness is expected to summarize their opinions, and usually, this is undertaken through claim analysis to indicate whether the claim is valid or not.[xi] Common sections of the patent law that are relied upon include sections 102[xii], 103[xiii], and 112.[xiv] The expert witness should be able to understand and apply a high-level review of these sections of the patent code from memory, as they turn up in a majority of IPR proceedings.

Grounds for Invalidation/Validation

An expert witness needs to be able to bring more than one piece of art together to form a ground. The incorporation of different technical pieces of art—such as patents, publications, textbook chapters, or other documents—should be done in a way that a POSITA at the time of the invention could use to implement and demonstrate the invention. The difficulty here is that the expert witness must effectively show that the invention in question is something a POSITA would be able to implement and ultimately invent. Careful selection of technical material to form a ground is critical in the IPR process, and the development of grounds requires comprehensive discussions with counsel.

IPR Depositions: A “Paper Trial”

Once the expert has written the expert opinion/declaration, opposing counsel has an opportunity to depose[xv] the witness.[xvi] This oral cross examination of the expert is usually considered a “paper trial,” and from the author’s perspective, it can determine the outcome of an IPR case—the expert witness’ answers can easily give strength to either side.

As such, experts should try to avoid giving “sound bites,” but that is easier said than done.[xvii] In general, the expert witness should answer all questions truthfully and to the best of their ability, as a responsive answer is always required. It is important to observe the style and type of questioning. While this author looks to depositions as a sort of “verbal chess,” the answers must directly relate to what has been written in the expert report.[xviii]

Experts also need to be aware of cross-examination strategies when in a deposition. Many of the most important questions come during the last hour, so it is important to watch for fatigue late in the proceeding or after meals; tiredness may weaken an expert witness’ quality of answers to questions.[xix],[xx] The expert should remain calm and collected, even if opposing counsel is being aggressive and bullying the witness with strong and loud language.[xxi],[xxii]

While there are several scenarios for expert witnesses in depositions, the IPR process is reasonably well organized for this part of the process. Still, the author has observed over the past 12 years that both counsel and expert witnesses thrive in oral proceedings. The cost to implement them might be high, but it could potentially become a reasonable economic threshold for those patent owners who sincerely want to defend their position. Oral trial testimony would add expense but would distinguish between a half-hearted IPR process[xxiii] and one that is important to litigate and requires full attention and focus.

In Summary

Expert witnesses are critical for the inter partes review process, and their opinions and performance in depositions can make or break cases between patent owners. The expert witness needs to comprehend and apply key legal standards to an IPR process in a way that allows for logical reasoning. Presently, oral arguments are not part of the procedure, but they are reasonably efficient to implement and would streamline the IPR process while adding to the skill base of expert witnesses. In general, the more IPR cases an expert witness engages in, the more experience they will have with differing situations—be it composing grounds, defining a POSITA, or participating in depositions. This experience benefits the expert as well as counsel.

The author Michael Lebby, B.Eng (Hons), MBA, Ph.D., D.Eng, C.Eng, FIEEE, FNAI, FOSA is the principal in Oculi, LLC, a San Francisco-based company that provides international board-level advisory, consulting, technological, and business-based services in the optoelectronics, semiconductor, and telecommunications industries. He is also CEO of Lightwave Logic, Inc., a company that develops high-performance optical polymers for the communications industry.

Dr. Lebby is an expert witness with experience in more than 130 patent litigation cases and 50 depositions. Over the course of 13 years, he has enjoyed learning and participating in the IPR process to resolve disputes over contested patents.

References & Notes

[i] USPTO. “Inter Partes Review,” October 10, 2022.

[ii] Or the patent petitioner. When patent owner is discussed, petitioner is always included as an alternative.




[vi] A full list is usually detailed in an appendix or exhibit; however, it should list all the documents (including private searches, internet and otherwise) that the expert witness conducted both intrinsically as well as extrinsically to synthesize the declaration and create their opinions.









[xv] See Fed. R. Civ. P. 30(b)(1) at

[xvi] For most expert witnesses, these cross examinations are dreaded as they can last at least seven hours on record. While counsel usually informs expert witnesses that they are not memory tests, this author has experienced several times where opposing counsel has refused to let the expert witness being crossed to look at their declaration or expert report.

[xvii] Answering technical questions and stating technical opinions are things that expert witnesses tend to be able to do effectively, especially if the subject matter is within the expert’s experience base. The thing to watch is that the technical answers given need to be scientifically reasonable. What is being scientifically reasonable? The expert witness should not give an answer or an opinion that cannot be properly substantiated technically. While at times this author has experienced counsel wanting answers that technically were not appropriate or asking for technology to stretch a little further to fit claim terms, it is of most importance that the expert witness be transparent and advise counsel on the limitations of the technology at hand. In fact, most counsel representatives are usually sensitive to this issue as it can have a drastic effect on the probability of winning or losing an IPR case.

[xviii] Straying off subject and effectively “teaching” opposing counsel on generic technical issues that do not relate to the subject matter at hand usually offers the opposing team opportunities to attack the experts’ declaration in some form or another. This author tries to keep all deposition answers close to what was written in the declaration, and if not, at least tying an answer to where in the declaration the subject has been discussed.

[xix] “Preventing Nuclear Settlements at Deposition: The Role of Cognitive Fatigue on Witness Performance | IADC,” n.d.

[xx] Fisher, Alison. “Why Do People Feel Tired after Eating?,” January 9, 2020.

[xxi] “Bad Deposition Conduct and Its Consequences,” n.d.,

[xxii] The difficulty here is being able to stay calm and collected. Generally, if you feel that the situation is being escalated, and some opposing attorneys have this as a strategy, and your own counsel is not being effective (and sometimes this is the case), then simply request (or demand) a break. Be aware that if there is a question pending, then a responsive answer needs to be given before a break is normally permitted. This author always tries to convey that there will be a responsive answer to a pending question in any situation, even if the opposing attorney may or may not like the responsive answer.

[xxiii] “Half-hearted” is a perspective that this author has seen in IPR cases where the seriousness of the litigation is seen to be weak and chaotic. There have been situations where patent owners initiate an IPR process just to find out if the patents they own and the associated issued claims are worth any value. Using the IPR process for valuation seems an inefficient use of resources. Yet, from the author’s observation, this is a rising trend.