Whether a patent can be invalidated without notifying the patent owner about the specific invalidity challenge and giving the patent owner an opportunity to be heard

QUESTION PRESENTED FOR REVIEW A patent claim is presumed to be valid. However, the patent claim’s validity can be challenged on the grounds that it lacks adequate written description in the patent application from which the claim issued (“the relevant patent application”). Separately, the same patent claim’s effective filing date can be challenged (without challenging the claim’s validity) for lack of adequate written description in an earlier filed “parent” patent application. The parent and the relevant patent applications have different written descriptions because their respective initially filed claims, which conclude the specification, are different. In the proceedings below, only the effective filing date was challenged, not validity. Yet, the Federal Circuit held that because both the filing date and the validity challenges relate to written description, Petitioner was put on notice and waived the argument that the initially filed claims of the relevant patent application provide verbatim written description support for the asserted claims. In view of this, the Question Presented is: Whether, as a matter of law and procedural due process, a patent can be invalidated without notifying the patent owner about the specific invalidity challenge posed by the validity challenger and giving the patent owner an opportunity to be heard.