An adverse decision in an IPR estops a Petitioner/accused infringer from raising certain invalidity defenses. What defenses are potentially affected?

The petitioner who loses an IPR will be estopped from raising any issues in district court (and the ITC) that it raised or reasonably could have raised in the IPR.

IPR is limited to patentability attacks under §§ 102/103 using patents and printed publications. Therefore, the estoppels are likewise limited to §§ 102/103 invalidity defenses based on patents and printed publications. By statute a petitioner cannot use evidence of a § 102(b) prior sale or public use in an IPR, and thus the petitioner will not be estopped from using that prior sale or public use in court.