The U.S., unlike many foreign patent offices, has a Duty of Disclosure (Rule 56 in the Patent Office Rules of Practice) that requires disclosure of information that a reasonable patent examiner would consider material to the examination of claims in pending patent applications. Information is submitted in the form of an Information Disclosure Statement. Failure to comply with the Duty of Disclosure can result in the resulting patent being unenforceable. Zealous compliance has often resulted in patent examiners being inundated with technical references. Too much disclosure has proven to be almost more of a problem than too little. Similarly, in litigation, allegations of inequitable conduct have consumed inordinate amounts of judicial resources.

The Therasense decision adopts what may be termed the “no way” test for inequitable conduct. Information that was not disclosed is judged to be “material” if there is “no way,” were the information to have been considered, that the patent would have issued with claims as it did. Intent to deceive the Patent Office is found if, based on a preponderance of the evidence, there is “no way” (no reasonable way to conclude) that the applicant or representative did not intend to deceive. Both materiality and intent to deceive must be present for inequitable conduct (and hence patent unenforceability) to be found.