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When in doubt, spell it out: Complying with a patentee's duty of disclosure

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U.S. patent laws require applicants and those involved with the filing and prosecution of a patent application disclose any information which may be material to patentability (i.e., whether a patent should be granted). Failure to disclose material information can result in a determination that the patent is invalid due to inequitable conduct.

A recent decision by the U.S. Court of Appeals for the Federal Circuit (the appellate court for patent cases), captioned Cargill Inc. v. Canbra Foods, Ltd. (06-1265, Feb. 14, 2007), involved Cargill's allegations that Canbra infringed four patents relating to a canola oil with reduced odors during storage and improved oxidative stability during cooking. During the prosecution of the patents in question, after a rejection by the patent examiner, Cargill successfully distinguished its patent applications from the prior art by arguing the test data within the Cargill patent application refuted the examiner's position. The patent applications were eventually allowed after several office actions and responses.

After Cargill sued Canbra and other parties for patent infringement, it was learned Cargill had failed to disclose a report and test data that was inconsistent with the position taken by Cargill during the prosecution of the patents. The district court found Cargill's failure to cite this information constituted inequitable conduct, and as a result, such patents were invalid and unenforceable.

On appeal, Cargill argued the report was not material to patentability, as the underlying tests were performed under unusual conditions. The Federal Circuit affirmed the unenforceability holding of the district court, stating "there is no such thing as a good faith intent to deceive. When an applicant knows or obviously should know that information would be material to the examiner, as was true here, but the applicant decides to withhold that information, 'good faith' does not negate an intent to manipulate the evidence."

The Cargill decision suggests the prudent course of action during the prosecution of a patent application is to cite anything that can be reasonably argued as being material to the Patent Office, whether such subject matter would render the underlying invention unpatentable. A subjective "good faith" belief that a reference or other disclosure is not material to patentability may not be sufficient to overcome a finding of inequitable conduct.

Compliance with the duty of disclosure requires ongoing diligence to determine whether there has been any recently obtained information that could be considered material. By ensuring those involved with the prosecution of a patent application -- for example, the inventors and their managers, in-house patent attorneys and the like -- promptly identify any prior art to their outside patent counsel, the enforceability of a patent can be improved and costly aspects of patent litigation minimized or even avoided.


Kukkonen is a Partner of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo PC, with a practice focusing on intellectual property including strategic counseling and patent prosecution.

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