May 27, 2011 – A decision by the Federal Circuit Court of Appeals in the Therasense v. Becton case on May 25th changed the standard of proof for materiality in inequitable conduct cases to a more stringent “but for” standard.  According to the ruling, undisclosed prior art meets the materiality standard for inequitable conduct only if it can be established that the PTO would not have allowed the claim had it been aware of the undisclosed art.