Federal Circuit Decision Suggests Patent Prosecutors Should Think Twice When Citing References

Most patent prosecutors err on the side of caution when deciding whether to cite prior art references to the United States Patent and Trademark Office (USPTO). Indeed, the consequence of not citing known prior art can be a finding during patent litigation that there was a violation of the USPTO’s duty of disclosure amounting to inequitable conduct, with the patent thereby being deemed unenforceable. But the United States Court of Appeals the Federal Circuit’s recent decision in Elekta Limited v. Zap Surgical Systems (Case 2021-1985, September 21, 2023) suggests that patent prosecutors should think about ways that the fact that references are being cited could be used against the patent owner, and prosecutors might consider clarifying the record to negate potential inferences being drawn based on the citation of references.

The patent at issue in Elekta claimed a device for treating patients with ionizing radiation. The Federal Circuit affirmed an inter partes review decision of the Patent Trial and Appeal Board (PTAB) that the claimed devices would have been obvious to one of ordinary skill in the art in view of a primary reference, “Grady,” and secondary references, including “Ruchala.” The Grady reference was directed to a radiation imaging device, whereas the Ruchala reference was directed to a radiation treatment device that included a linear accelerator, or “linac.” One of the issues in the case was whether one of ordinary skill in the art would have been motivated to use a linac as in Ruchala’s treatment device in the imaging device taught by Grady. The patent owner argued that the skilled artisan would not have found it obvious to make the modification because the weight of the linac would render the imaging device taught by Grady essentially inoperable and thereby fail to provide a viable solution for focusing therapeutic radiation on the target. The Federal Circuit, however, found that there was substantial evidence supporting the PTAB’s finding that heavy linacs were known in the art and that their weight could be adequately handled by robotic arms like those found in Grady’s treatment device.

Silence Kills

In its analysis, the court cited to a PTAB finding that the prosecution history of the patent included submission and discussion of references directed to imaging devices, and that the applicant did not argue that the imaging device references were not relevant art. Elekta, Slip Op. at 9. Looking into the prosecution history referred to by the court and the PTAB, imaging devices were cited and/or discussed in three instances: the applicant cited a reference directed to an imaging device in an information disclosure statement (IDS), the Examiner cited a reference directed to another imaging device in a prior art rejection, and the Examiner cited a third reference directed to an imaging device in a statement of reasons for allowance. As is common practice, the applicant did not provide any comments about the imaging device reference when submitting the IDS. Regarding the imaging reference cited in the prior art rejection, the applicant distinguished the reference based on certain features, but did not argue that the reference was irrelevant because it was directed to a radiation imaging device rather than a radiation treatment device. The applicant also did not file any comments on the imaging device reference referred to in the Examiner’s statement of reasons for allowance. The court and PTAB in essence found that the applicant’s silence during prosecution amounted to an admission that radiation imaging devices were relevant art to be considered in combination with radiation treatment devices.

It is notable that the PTAB’s decision itself did not predominantly rely on the fact that radiation imaging device references were cited during the prosecution history as a basis for reaching its conclusion that there was a motivation to combine imaging and treatment device references. While the PTAB decision did refer to the petitioner’s arguments on the prosecution history regarding treatment devices, the PTAB largely focused on a determination of the pertinent field as being related to general engineering design and the testimony of the petitioner’s expert as to the viability of the combination of references. The Federal Circuit’s decision also discussed the aspects of the PTAB’s decision relating to the pertinent field and expert testimony. But the Federal Circuit’s specific citation to the prosecution history part of the PTAB’s decision indicates that the court found the facts as to the submission and discussion of radiation treatment devices as being significant.

It is also notable that the findings of the court and PTAB that the applicant’s silence was an admission that the references were relevant appears to be in tension with the 37 C.F.R. § 1.97(h). That rule states that the “filing of an information disclosure statement shall not be construed to be an admission that the information cited in the statement is, or is considered to be, material to patentability[.]” In an analogous context, the Federal Circuit has held that the listing of a patent in an IDS does not make the patent available as prior art absent an actual statutory basis (e.g., the reference is applicable under 35 U.S.C. § 102). Riverwood Int’l Corp. v. R.A. Jones & Co., 324 F.3d 1346 (Fed. Cir. 2003). There did not appear to be consideration of an argument in the Elekta case that the applicant’s lack of comments on the references did not amount to an admission as to their relevancy.

Ways Forward

Could a result as in Elekta be avoided with some sort of applicant statement at the time references are cited or otherwise discussed during prosecution? Perhaps. Applicants are free to comment on a reference anytime that they submit an IDS, and applicants can freely comment on a reference that is cited in a prior art rejection. Further, USPTO procedure specifically allows for applicants to file comments on an examiner’s statements of reasons for allowance. But the general rule that many patent prosecutors follow is to say as little as possible on the record. And so, references are usually cited in IDSs without substantive comments, and references are discussed to the least extent possible when responding to a prior art rejection. Given the court’s analysis in the Elekta case, prosecutors may need to rethink the strategy of avoiding any discussion of references. For example, an approach that might be helpful is making a statement that the applicant does not admit that the references cited in an IDS are relevant to the claimed invention. Such a statement could perhaps be bolstered by express reference to Rule 197(h).

At the very least, the Elekta decision indicates that patent prosecutors need to carefully consider how the mere citation of a reference during prosecution could be relevant. While the prosecutors will no doubt continue to err on the side of caution when it comes to citing references in IDSs, it may be the case that further statements should be made in the record to avoid implications such as those found in Elekta.

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