For over a decade, the inequitable conduct defense to patent infringement has been regarded as a somewhat disfavored defense. Indeed, nearly 20 years ago, the Federal Circuit expressed its distaste for the assertion of the defense in nearly every patent infringement suit, and issued an opinion that served to curtail a district court’s discretion to find inequitable conduct. Where the basis

of an inequitable conduct allegation was false statements or omissions made in affidavits submitted to the United States Patent and Trademark Office (“PTO”), however, district courts were afforded somewhat broader discretion to find that inequitable conduct had occurred.

Recent developments in Federal Circuit case law have confirmed the vitality of the inequitable conduct defense, particularly where the basis for the defense is misstatements or omissions made in affidavits submitted to the PTO. In cases involving affidavits, recent Federal Circuit opinions have established that district courts have broad discretion to find inequitable conduct, and, in particular, “intent to deceive the PTO.” Patent applicants thus must exercise special caution when submitting

affidavits to the PTO.