IPR estoppel can be kind of terrifying as an accused infringer in a patent action. The statute says that an accused infringer may not assert invalidity on a ground that it could have raised in the IPR; but you can't raise product prior art, so product prior art should be safe, right?
Nope. Courts have sometimes held that product prior art may still be estopped, if there is patent or written prior art that is sufficiently similar. See, e.g., Wasica Fin. GmbH v. Schrader Int’l, 432 F. Supp. 3d 448, 453 (D. Del. 2020) (holding defendant estopped from asserting product art where “all the relevant features” of the art were in a printed publication that could have been raised in an IPR).
As Judge Stark notes in Wasica, courts have gone both ways on this, with some estopping arguments based on product art where similar written or patent art could have been raised in an IPR, and others permitting those arguments.
On Friday, Judge Noreika chose a side in this split: no estoppel for prior art products ...