By Dennis Crouch
Normal rule is that when a court finds a patent invalid that the patentee will be estopped from attempting to enforce the patent against any other party. This is the rule that arises from Blonder-Tongue Labs., Inc. v. University of Illinois Foundation, 402 U.S. 313 (1971).
My question: Would this collateral estoppel continue to apply if the patent owner was able to show that it lost the prior case because of attorney negligence rather than because the patent was actually invalid? In criminal and class action cases this sort of inadequate representation argument regularly wins with the support of the due process clause of the constitution. But, a patent infringement lawsuit is somewhat different. However, a key to the Blonder-Tongue decision is the assumption that in the originally case "the plaintiff had fully and fairly, but unsuccessfully, litigated same [validity] claim in the prior suit." It is hard to say that the claim was fully and fairly litigated if its lack of success was due to attorney malpractice.
The outcome of this question is likely to have some impact on the Gunn v. Minton patent litigation malpractice case that was recently argued at the Supreme Court. In particular, if proof of inadequate representation can clear the patent then there is a much stronger case that the malpractice claim raises substantial issues of patent law.