The doctrine of marking estoppel would conflict with the normal evidentiary treatment of [extrajudicial admissions of fact, and we] decline to adopt a special equitable doctrine for [their] treatment.

On March 15, 2013, in Frolow v. Wilson Sporting Goods Co., the U.S. Court of Appeals for the Federal Circuit (Newman, Clevenger, Moore*) affirmed-in-part, reversed-in-part and remanded the district court's summary judgment that Wilson did not breach the license agreement with Frolow and did not infringe U.S. Reissue Patent No. RE33,372, which related to tennis rackets. The Federal Circuit stated:

Under the doctrine of "marking estoppel" recognized in some circuits, "a party that marks its product with a patent number is estopped from asserting that the product is not covered by the patent." [T]he Supreme Court has never adopted or approved the doctrine. Mr. Frolow asks us to adopt this doctrine and to hold that Wilson is estopped from arguing that its fourteen marked rackets fall outside the '372 patent claims. We decline to create a separate, equitable doctrine unique to patent law, where Congress has spoken and standard evidentiary practices provide adequate remedy.

Congress enacted legislation, recently amended, which provides a remedy for false marking. Marking estoppel cases explain that the rationale for the doctrine is to prevent harm to the public which might be caused by mismarking. But Congress expressly addressed this exact harm and crafted a remedy which it determined was appropriate to remedy any harm to would-be competitors or innovators. Congress sought to protect the public from false marking by providing a remedy in the form of civil damages to persons "who ha[ve] suffered a competitive injury as a result of" improper patent marking. If the mismarking was done "with the intent . . . of deceiving the public" or some similar specific intent, the statute provides for recovery under either the civil damages provision (by an injured competitor) or the penalty provision (by the United States). Equity should not rush in where an adequate remedy at law exists. It would be inconsistent with this legislation to adopt a different and broader remedy for the same harm.

Although we do not endorse Mr. Frolow's patent marking doctrine, we do agree that the fact that Wilson marked their products with his patent number is a fact which supports his allegation that Wilson's products fall within the patent claims. The practice of marking a product with a patent number is a form of extrajudicial admission that the product falls within the patent claims. Extrajudicial admissions of fact are statements made by a party outside the context of the litigation that are introduced into evidence by that party's opponent. Generally, extrajudicial admissions of facts, such as patent marking, are simply evidence that may be countered by the party that made the admission. These admissions are not "binding," and "may be controverted or explained by the party" that made the statement. The doctrine of marking estoppel would conflict with the normal evidentiary treatment of these sorts of admissions. We decline to adopt a special equitable doctrine for the treatment of these "admissions.

In this case, the district court erred when it held that the defendant's marking was irrelevant. Placing a patent number on a product is an admission by the marking party that the marked product falls within the scope of the patent claims. The act of marking is akin to a corporate officer admitting in a letter or at a deposition that the company's product infringes a patent. A defendant, of course, is free to introduce counter evidence or explanation. Thus, the district court erred when it concluded that Wilson's marking had "no bearing on whether literal or doctrine of equivalents infringement has occurred." Like any other type of extrajudicial admission, evidence of marking is relevant evidence. And such an admission, that the accused product falls within the asserted claims, is certainly relevant on the issue of infringement. Of course, whether a party's marking, in view of the record as a whole, raises a genuine issue of material fact, will depend on the facts of each case. . . .

We conclude that in this case, where Mr. Frolow contested whether the rackets fall within the scope of the claims and provided evidence of marking, that summary judgment is improper. To be clear, we are not holding that the fact of marking alone is enough to survive summary judgment in every case. If a patentee admits that the accused product does not infringe, evidence of marking will not raise a genuine issue of material fact. Similarly, if it is beyond dispute that the accused product was mismarked, summary judgment will be appropriate. But evidence of product falls within the patent claims and can preclude summary judgment in appropriate cases. Accordingly, the district court erred when it concluded that Wilson's marking had "no bearing" on whether the rackets were Licensed Articles.

It is hornbook law that a patentee may prove an issue of fact "by either direct or circumstantial evidence." Indeed, "circumstantial evidence is not only sufficient, but may also be more certain, satisfying and persuasive than direct evidence." In reviewing the evidence, our task is to discern whether "the record taken as a whole could not lead a rational trier of fact to find for the non-moving party." The evidence in this case points in both directions. Wilson's expert report tends to show that its rackets are not Licensed Articles and Mr. Frolow's evidence of marking tends to show that those rackets are Licensed Articles. It is the job of the fact-finder -- not the court at summary judgment -- to weigh that evidence and render a decision. We therefore reverse the court's grant of summary judgment and remand for further proceedings.