Inequitable conduct, often called “fraud upon the patent office,” generally means that in trying to obtain a patent, the applicant was not honest with the patent office and failed to disclose prior art or other information known by the applicant that was material to the patentability of his/her invention. Patent prosecution rules include a Duty of Candor, which requires the applicant and his/her representatives to disclose material information to the USPTO during prosecution of the patent application. Should an applicant withhold material information and thus commit inequitable conduct, the result is that the patent would be deemed unenforceable. This is an equitable doctrine. It means that even if the patent is valid, the applicant would be precluded from enforcing it against infringers due to the fraud upon the patent office. Inequitable conduct is a defense sometimes raised to allegations of infringement.
The court has also recently created a heightened test for proving materiality. The court has employed a “but for” standard for proving materiality. The test requires a showing that the patent would not have issued but for the alleged material act. For a prior art reference, the showing requires that the patent claims would not have been allowed by the patent examiner had the examiner considered the withheld reference during prosecution.
No longer may inequitable conduct be based upon a mere failure to disclose prior art to the USPTO, where intent may be inferred from a reference that is on point to the patentability of the pending claims. This trend to heighten the standards of proof required for a showing of inequitable conduct aligns with the idea that the courts do not really like this defense and believe that it should be reserved for instances of egregious conduct. Still, it is advisable for an inventor to disclose all prior art and information of which the applicant is aware which may be material to the patentability of his/her application.