I. Introduction

Given the limited scope of evidence available in PTAB trials, expert evidence is perhaps second in importance and prominence only to the petition itself. This article provides observations from recent cases as to how to both persuasively use expert evidence and to attack it.

First, note that expert evidence can be presented at nearly every stage of a PTAB trial, both before and after institution. In particular, as a result of a recent rule change, both petitioners and patent owners can now submit expert evidence in their pre-institution filings.1 Further, the patent owner’s response and the petitioner’s reply may also include expert affidavits.2 Sur-replies, if granted, can also include expert affidavits. Deposition of experts is considered routine discovery.3 Even after all the substantive papers have been filed, cross-examination observations can be filed (upon obtaining approval) to highlight useful expert testimony. The PTAB, however, is not likely to hear live expert testimony at the trial’s hearing, because an expert’s credibility is typically not ascertained by observing her demeanor.4

II. Strategic Considerations

A. Persuasive Expert Testimony

Unlike jurors in a district court, PTAB judges typically have technical degrees and substantial experience evaluating patentability based on technical references. Thus, it is important to consider how an expert can be persuasive at the PTAB.

An expert can persuasively “fill in the gap” where a reference may be silent or incomplete. For example, the PTAB found expert testimony by a librarian persuasive when it was used to establish the authenticity of nearly 20-year old documents.5 One document was a 1995 paper published by an Australian university, and the other was a 1995 letter submitted to the IEEE Transactions on Communications.6 Petitioner attempted to authenticate the documents by having a librarian state that they were available online from the Australian university’s website and by relying on an e-mail from the manager of the website.7 The librarian also opined that the documents were “in a condition that creates no suspicion about their authenticity and that they are in a place where, if authentic, they would likely be.”8 Patent Owner attacked the librarian’s opinion because he allegedly did not have sufficient personal knowledge to authenticate the documents and was not a custodian of the documents.9 Petitioner countered by arguing that the librarian was an expert who was qualified to opine about the authenticity of the documents and that he may base his opinion on facts or data that need not otherwise be admissible.10 The librarian’s unrebutted opinion was relied upon by the Board’s decision to find the documents sufficiently authentic.11 Further, the librarian’s unrebutted observations were found helpful to establish their availability at the time of the invention in view of the fact that the authors were Australian: “it would have been difficult to procure superior evidence, such as compelled testimony, through reasonable efforts.”12

Another area where experts are heavily relied upon by PTAB judges is on the issue of inherency. While PTAB judges have technical experience, they are quick to rely on experts when the technical questions become complex or detailed beyond their experience level. For example, a few months ago the PTAB issued a final decision canceling claims after heavily relying on the petitioner’s expert to make inferences about the teachings of the prior art.13 In that case, the question before the PTAB was whether a prior art reference that taught an algorithm involving “concatenation” anticipated a claim requiring an algorithm involving “summation.”14 The reference did not explain how concatenation was performed.15 Both experts agreed that there were two ways of performing concatenation and that one of those ways did not involve summation as required by the claims.16 Petitioner’s expert convinced the Board that the reference taught performing concatenation using summation, because the expert identified teachings in the reference that supported this inference; in particular, the expert identified that the stated programming language, stated programming structure, and stated goal of a small number of lines of code all led to the inference that the manner of implementing concatenation using summation was contemplated by the reference.17 Patent Owner failed to provide expert testimony to rebut these opinions.18 This case highlights an important distinction between effective use of experts at the PTAB compared to district court litigation. Such complex arguments may overwhelm a jury (and possibly a district court judge), but the PTAB judges’ technical acumen provide parties an opportunity to put forth detailed expert opinions to convince the judges on the panel.

The importance of paying close attention to expert testimony in inherency arguments is particularly highlighted by the PTAB’s refusal to credit such arguments without appropriate expert testimony. For example, the PTAB has rejected a party’s inherency argument because the expert testimony was insufficient and conclusory.19 The claims in that case required a fabric that included a thermal property called “thermal protective performance” (“TPP”) value of at least 4.5.20 The references relied upon by Petitioner did not address the TPP value of the fabrics they disclosed, and the only timely evidence submitted was expert testimony that explained that the TPP value is a result of characteristics of the fabric without explaining why the combination of references would have the claimed TPP value.21 Further, Patent Owner put forth expert testimony explaining why the references would not yield a fabric with the claimed TPP value.22 The claims were held not to be obvious.23 24

These observations apply to other contexts as well. The PTAB has reacted similarly to issues stemming from an obviousness inquiry. Expert opinion has become almost expected in areas such as rationale for combining references, the state of the art at the time of the invention, and indicia of non-obviousness.25 Another area where experts can be persuasive (within limits) is claim construction: “[e]xpert testimony is useful to explain terms of art, and the state of the art at any given time, but cannot be used to prove ‘the proper or legal construction of any instrument of writing.’”26 Last, determining the level of ordinary skill in the art is a matter for which the PTAB has looked to experts for guidance.27

B. Discounted Expert Testimony

Surveying recent cases reveals a consistent message from the PTAB: unsupported opinions are a waste of the parties’ time and resources. “Expert testimony that does not disclose the underlying facts or data on which the opinion is based is entitled to little or no weight.”28 For example, earlier this year the PTAB denied institution of an inter partes review, and expert testimony addressing both claim construction and applying prior art was rejected.29 “[T]he cited expert testimony merely repeats the Petitioner’s conclusory argument, adding the phrase ‘[i]n my opinion[.]’”30 Here, the Petitioner failed to take advantage of the expert declaration to further explain positions taken in the page-limited petition. And this was particularly important where Petitioner faced an uphill battle: arguing that “subset” could include the entirety of a set rather than just a portion of it in both claim construction and the prior art.31

Even if expert testimony is used to further explain a party’s position, the PTAB requires experts to identify direct support for their opinions. For example, in a final decision favoring Petitioner earlier this year, the PTAB discounted Patent Owner’s expert’s testimony three different times. Patent Owner’s expert disputed the propriety of combining references because: (1) there was no expectation of success of the combination; (2) the combination would require “dramatic changes” beyond the skill of an ordinary artisan; (3) the combination would require undue experimentation.32 While these bases can be persuasive to reject a proposed prior art combination, the expert failed to properly support them. Regarding the first basis, the expert opined that experiments based on one reference’s teaching would have little applicability to the “real world.”33 But this was discounted because the expert did not provide any comparative data or other evidence to support his opinion.34 While the expert did provide some evidence for the second and third bases, the judges discounted the testimony because the evidence was not directly relevant to the expert’s opinion. For the second basis, the expert relied on a handbook that discussed error rates that would require “dramatic changes” to overcome; but the PTAB found that the error rates discussed in the handbook were directed to a different type of wireless transmission than the one at issue.35 As to the third basis, the PTAB discounted the expert’s opinion on undue experimentation because the evidence merely alleged differences between the two prior art references.36 This is not the only case where the PTAB has taken a careful look at how an expert supports her opinions.37 Thus, it must be appreciated that PTAB judges carefully examine the evidence upon which experts rely and decide to discount the testimony if it does not appear supported.

C. Excluding Expert Testimony

Excluding expert testimony from jury trials has several familiar bases: improper qualifications, improper methodology or basis, or otherwise unhelpful to the trier of fact.38 PTAB judges have both legal and technical backgrounds, and that has affected the exclusion of expert testimony in PTAB proceedings. In particular, the PTAB has been reticent to exclude expert testimony based on qualifications or improper methodology; rather, the PTAB appears to prefer exercising its discretion to accord “little or no weight” to improper expert testimony.39

An important exception to this trend is untimely declarations. The rules of PTAB proceedings create a timed sequence of disclosures wherein parties must disclose all the evidence on which they want to rely.40 Expert declarations served in later stages of the proceedings that could have been served earlier have been excluded. For example, the PTAB excluded an expert declaration served with the Petitioner’s Reply because it should have been part of the initial petition.41 There the issue was whether the combination of references resulted in a fabric that would necessarily have a claimed thermal characteristic (“thermal protective performance” or “TPP”).42 Patent Owner pointed out that the petition did not explain why the claimed characteristic would be inherent to the fabric resulting from combining the references.43 In response, Petitioner’s Reply included a new expert declaration addressing this issue.44 But the Board found this denied Patent Owner an opportunity to file responsive evidence and that Petitioner could have presented the evidence in its petition.45

III. Conclusion

Expert testimony is an important factor in PTAB proceedings. The fact that PTAB judges typically have both legal and technical backgrounds requires viewing expert evidence differently than what is typical in district court. A party should carefully plan how expert testimony will be used in its case. Complete analysis in the preliminary filings can be crucial to preserving arguments throughout the trial. Expert declarations should be scrutinized carefully for objections, and depositions should be carefully planned to expose any weaknesses in the expert’s opinions. The acumen of PTAB judges provides both petitioners and patent owners with opportunities to present highly technical arguments that parties would not otherwise have presented in district court.