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Federal Circuit Restricts Inequitable Conduct Doctrine

Intellectual Property Law Update Steven J. Wietrzny

On May 25, 2011, in Therasense, Inc. v. Becton, Dickinson and Co., an en banc panel for the Court of Appeals for the Federal Circuit made it more difficult for an accused infringer to prove a patent unenforceable based on inequitable conduct by the patentee. Under the new standard, an accused infringer must show that the patentee knew of a reference, knew that the reference was material, and intentionally or deliberately failed to submit the reference. Both materiality and intent must be proven by clear and convincing evidence.

Although the Therasense decision does not change the duty of candor owed to the Patent Office while prosecuting a patent, the decision will make it easier for patent applicants to comply with disclosure requirements.


Under the Therasense decision, a prior art reference known to the patentee, and that was not submitted to the U.S. Patent Office when the application was examined must be shown to be "but for" material ("but for" the absence of that reference, the examiner would not have allowed the claims of the patent) to establish inequitable conduct by the patentee. The omission must also be truly intentional. These changes to the law of inequitable conduct in the courtroom, however, do not change the duty of candor to the Patent Office during prosecution of the application.


With respect to materiality, the Court adopted the "but-for" test and expressly rejected the standard for materiality as it is defined in Rule 56 (37 C.F.R. ยง 1.56), which governs an applicant's duty of candor to the Patent Office. Under the more stringent "but for" test, a reference that is withheld from the Patent Office is considered material if the patent examiner would not have allowed. Accordingly, in court a defendant will be less likely to prove inequitable conduct, and render a patent unenforceable, based on failure to submit prior art that does not otherwise invalidate the patent on the merits.


The Court also held that to show intent to deceive the Patent Office a defendant must prove that the patentee knew of the prior art, knew the prior art was material, and made a deliberate decision to withhold the prior art from the Patent Office. The Federal Circuit expressly rejected a negligence standard in which the required intent could be established if the patentee merely should have known about the materiality of the omitted prior art. The Court confirmed that intent to deceive may be inferred from indirect and circumstantial evidence, but only when it was the singular reasonable inference.

Duty of Candor to the Patent Office

Although Therasense addresses the doctrine of inequitable conduct from a litigation standpoint, the decision does not change the duty of candor owed to the Patent Office while prosecuting an application under Rule 56.

Under Rule 56, inventors, prosecuting attorneys or agents, and any person substantively involved in the application process have a duty to disclose to the Patent Office all the information that they are aware of that is material to patentability of the invention during the prosecution of a patent application. The Patent Office defines information to be material to patentability if the information is not cumulative to information already on the record for the application and either (a) establishes a prima facie case of unpatentability of a claim in the application; or (b) refutes, or is inconsistent with, a position the applicant takes with regard to the patentability of one or more claims before the Patent Office. This standard of materiality before the Patent Office is thus more encompassing than the "but-for" standard of materiality in the courtroom.

Although the broader Rule 56 standard still applies, the Therasense decision should provide some measure of comfort to individuals involved in prosecuting patents. The Federal Circuit makes clear that a patentee cannot possess the requisite intent to deceive the Patent Office by merely failing to submit material prior art that the patentee was not aware of, but should have been aware of. Thus, those involved in prosecuting an application need not take extraordinary measures to become aware of potentially material references. The Federal Circuit even noted that such practice resulted in flooding the Patent Office with amounts information that strain its resources and contribute to its backlog.


The Federal Circuit's decision in Therasense restrains the inequitable conduct doctrine in court by requiring defendants to prove "but for" materiality and intent to deceive the Patent Office. The decision does not change the duty of candor before the Patent Office, which remains as outlined by Rule 56. Therefore, individuals involved in prosecuting patent applications must continue to disclose material references that they are actually aware of, but without being burdened by art that they "should have known about."

The Patent Office has already issued a press release indicating that they expect to issue further guidance to applicants in the near future. Although it is not clear what the new guidelines will suggest, it is likely that the Patent Office will attempt to limit submissions to the Patent Office, and therefore make it easier for patent examiners to review the most relevant prior art.

For more information on the Therasense decision or other patent matters, please contact Steven Wietrzny at (414) 277-5415 / [email protected] or your local Quarles & Brady attorney.

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