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US patent practice update: duty of candor and inequitable conduct

25th May 2011

When prosecuting a patent application at the US Patent and Trade Mark Office (USPTO), there is a duty of candor and good faith that extends to each individual associated with the application. If it is shown during patent litigation that an individual intended to deceive the USPTO during prosecution of a patent application from which a patent granted, it is deemed ‘inequitable conduct’. The penalty for such a finding is severe; the patent is entirely unenforceable.

The duty of candor and good faith includes a duty to disclose to the USPTO all information known to the individuals associated with the application to be “material to patentability”. Such information is entered onto the file of the US patent application as an Information Disclosure Statement. However, the extent of this duty has not been clearly defined, and this has led to a number of problems with prosecution and enforcement.

Clearly, for patent applicants, it is imperative for the duty of candor and good faith to be met. So, in recent times, patent applicants have typically filed a large number of prior art references (many of limited relevance), to ward off potential allegations from third parties that they have acted improperly. This has created a large workload at the USPTO. Also for accused infringers of US patents, making an allegation of inequitable conduct is a well-used defensive strategy in litigation. This has increased the cost and complexity of litigation as well as reducing the likelihood of settlement.

Where are the lines really drawn, and when does information start being “material to patentability? Additionally, what behaviour should be considered an intention to deceive to the USPTO, which is needed to be successful in showing inequitable conduct?

These questions have been answered recently inan important decision of the US Court of Appeals of the Federal circuit in Therasense, Inc v Becton, Dickinson & Company.

Significantly, the decision “tightens the standards”. The decision states that to show intention to deceive, “the accused infringer must prove by clear and convincing evidence that the patent applicant knew of the [uncited] reference, knew that it was material, and made a deliberate decision to withhold it”. The decision takes the view that the level of materiality required to establish inequitable conduct is “but-for” materiality. In other words, to show that information is material to patentability, it must be shown that the USPTO would not have allowed a granted claim of a patent if they had been aware of the undisclosed information.

As a result, commentators expect fewer prior art references, and only those of clear relevance, to be filed at the USPTO during prosecution of US patent applications and allegations of inequitable conduct will be less likely to be contested during litigation. It seems a victory for commonsense, and it is hoped will lead to lower overhead for applicants and patentees. The USPTO are reviewing the decision and it is expected that they will issue a new guidance note in due course.

This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking before any action in reliance on it.

Robert Sackin
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