The Court of Appeals for the Federal Circuit held Wednesday that the doctrine of equivalents covers alternatives that were foreseeable at the time of application but not literally claimed. As a result, patent drafters will not be forced to draft claims to cover all foreseeable alternatives or risk losing coverage over even insubstantial modifications. The Federal Circuit also confirmed claim vitiation is not a legal exception to the doctrine of equivalents, thus reinforcing the difficulty of obtaining summary judgment of non-infringement by equivalents.


ARB Corp. Ltd., an Australian manufacturer of aftermarket off-road equipment, owns a patent covering a locking differential, the mechanical device that allows a car’s tires to spin at different rates so they don’t lose traction when turning. One of ARB’s former distributors, Ring & Pinion Service, told ARB that it planned to sell a knockoff of ARB’s differential, but slightly modified in an effort to avoid the ARB patent. ARB objected, and R&P filed suit in federal court in Seattle seeking a declaration that it did not infringe. After the court construed the relevant patent claim terms, R&P agreed its knockoff design infringed.

But this did not end the dispute. R&P then modified its knockoff differential in a further effort to avoid ARB’s patent. ARB responded that the modified differential still infringed its patent under the doctrine of equivalents, which gives a patent owner an opportunity to prove infringement even if a device falls outside the literal scope of the patent’s claims. Both ARB and R&P moved for summary judgment on whether the modified design infringed under the doctrine of equivalents.

In its argument to the trial court, R&P admitted its differential was an equivalent of what the patent claimed, but argued a “foreseeability” exception kept it from infringing under the doctrine of equivalents. According to R&P, because its modified design was foreseeable when ARB filed its patent application, but was not claimed in the patent, the doctrine of equivalents could not apply to it.

The trial court rejected ARB’s proposed foreseeability exception to the doctrine of equivalents, but nonetheless found no infringement under the doctrine of equivalents, holding that a finding of infringement would improperly “vitiate” an element in the patent claim. ARB appealed.

The Court rules for ARB

In a unanimous, precedential opinion, the Federal Circuit reversed, stating unequivocally that “[t]here is not, nor has there ever been, a foreseeability limitation on the application of the doctrine of equivalents.” With this ruling, the Federal Circuit turned its back on dicta in previous cases, starting with Sage Products, Inc. v. Devon Industries, Inc., 126 F.3d 1420 (Fed. Cir. 1997), and including three concurring opinions authored by Chief Judge Rader, Vehicular Techs. Corp. v. Titan Wheel Int’l, Inc., 212 F.3d 1377, 1383 (Fed. Cir. 2000) (Rader, J., concurring); Johnson & Johnston Assocs. v. R.E. Serv. Co., 285 F.3d 1046, 1056-63 (Fed. Cir. 2002) (Rader, J., and Mayer, C.J., concurring); and Siemens Med. Solutions U.S., Inc. v. Saint-Gobain Ceramics & Plastics, Inc., 647 F.3d 1373, 1376 (Fed. Cir. 2011) (Rader, C.J., Newman, J., Lourie, J., and Linn, J., concurring), that argued for recognizing a foreseeability exception to the doctrine of equivalents. In rejecting a foreseeability limitation, the Federal Circuit relied on case law that ARB presented to hold that such a limitation would conflict with long-standing Supreme Court and Federal Circuit precedent.

After rejecting R&P’s proposed foreseeability exception to the doctrine of equivalents, the Federal Circuit ruled that claim vitiation would not prevent R&P’s admittedly-equivalent product from infringing under the doctrine of equivalents. It therefore reversed the district court’s grant of summary judgment of non-infringement and remanded with instructions to enter an infringement ruling in favor of ARB.

Takeaway lesson

Wednesday’s ruling definitively resolved a potential ambiguity in the Federal Circuit’s cases, making clear that the doctrine of equivalents does not include a foreseeability bar. R&P’s proposed interpretation of Sage Products and Judge Rader’s concurrences would have imposed a substantial burden that many patent applicants would fail to meet. An absolute bar against foreseeable equivalents would have required an applicant to determine and describe, for each element of each patent claim, all alternatives known to any person of ordinary skill in the art, whether significant or insignificant. The applicant would further need to craft claims covering each of these potential alternative means of implementing each element, because any omission (irrespective of its significance) would fall outside the scope of the claims and could not be the basis for liability under the doctrine of equivalents. By rejecting R&P’s proposed foreseeability bar the Federal Circuit affirms that patent drafters need not inflate their claim sets in an attempt to carry this heavy burden.

In the litigation context, this ruling further emphasizes the overlap between the standard for summary judgment of non-infringement under the doctrine of equivalents and the claim vitiation doctrine. Notably, both look to whether a reasonable jury could find two elements to be equivalent. As a result, an accused infringer may not use claim vitiation as a legal shortcut that provides a more direct route to summary judgment of non-infringement. Rather, an accused infringer will need to focus its non-infringement arguments on whether the patent owner has established the factual basis for a finding of infringement under the doctrine of equivalents.