What are the limitations of res judicata in patent applications?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

Res judicata in patent applications has several limitations. According to MPEP 2190:

“A res judicata rejection should be applied only when the earlier decision was a decision of the Patent Trial and Appeal Board (or its predecessor Board) or any one of the reviewing courts and when there is no opportunity for further court review of the earlier decision.”

Additionally, res judicata may not apply if:

• The previously adjudicated and current claims are significantly different
• New evidence of patentability is provided
• The definition of a “final” Board decision has changed

These limitations ensure that res judicata is applied appropriately and does not unfairly prevent legitimate patent claims.