A recent Federal Circuit case reminds us how difficult it is for a patent holder to win an infringement case based on a doctrine of equivalents (DOE) infringement theory. In Jang v. Bos. Sci. Corp. & Scimed Life Sys., Inc., No. 16-1275 (Fed. Cir. Sep. 29, 2017), the Fed. Cir. affirmed the district court’s vacatur of the jury’s infringement verdict, finding that Boston Scientific Corporation’s (BSC) product did not infringe the asserted claims of Dr. Jang’s patent under the DOE because Dr. Jang did not meet his burden of proving that his DOE theory did not ensnare the prior art.
The DOE allows a patent holder to prove infringement by an accused device if the accused device performs substantially the same function as claimed in substantially the same way to obtain substantially the same result, even if it does not literally infringe the claims of the patent. Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 608-609 (1950). However, there is a concern that the DOE undercuts the notice function of a patent claim. See id. at 613-14 (Black, J., dissenting). The courts have come up with various ways of limiting the application of the DOE, including prosecution history estoppel (Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., 535 U.S. 722 (2002), holding that a patent holder cannot recapture subject matter that was given up during patent prosecution.), the public dedication rule (Johnson & Johnson Assocs., Inc. v. R.E. Service Co., Inc., 285 F.3d 1046 (Fed. Cir. 2002) (en banc), holding that subject matter that is disclosed but not claimed is public property), the all-limitations rule and specific exclusion rule (Scimed Life Systems, Inc. v. Advanced Cardiovascular Systems, Inc., 242 F.3d 1337 (Fed. Cir. 2001), holding that the DOE is applied to each limitation, not to the invention as a whole; and is unavailable to capture subject matter that the claim specifically excludes), and the ensnarement rule (Wilson Sporting Goods Co. v. David Geoffrey & Associates, 904 F.2d 677 (Fed. Cir. 1990), holding that claim coverage under the DOE cannot extend to include subject matter that forms part of the prior art). Jang demonstrates an example of the ensnarement rule.
The dispute between Dr. Jang and BSC involves U.S. Patent No. 5,922,021 (’021 Patent), which is generally directed to a coronary stent, and which was assigned to BSC by Dr. Jang in 2002. Jang, No. 16-1275 at 5-6 (Fed. Cir. Sep. 29, 2017). Pursuant to the assignment agreement, Dr. Jang was entitled to certain royalty payments if BSC ever developed and sold a coronary stent that was covered by (i.e., would infringe) the ’021 Patent. Id. at 6. In May 2005, Dr. Jang filed a suit against BSC for owed royalty payments, asserting that BSC’s product “Express Stent” was covered by claims 1 and 8 of the ’021 Patent. Id. The district court denied BSC’s invalidity defense, reasoning that BSC owed Dr. Jang royalty payments for past sales pursuant to the assignment agreement as long as the product was covered by the patent, even if the patent was declared invalid later.1 Id. at 7. The parties then proceeded to trial on infringement.
The jury found no literal infringement of the ’021 Patent, but found infringement under the DOE. Id. at 8. The district court then ordered a post-trial evidentiary hearing on BSC’s ensnarement defense where Dr. Jang bore the burden of showing that his range of equivalents did not ensnare the prior art. Id. At the hearing, Dr. Jang provided two hypothetical claims predicated on claim 1 of the ’021 Patent, each of which was broad enough to literally cover BSC’s Express stent, yet not so broad that it would be unpatentable over the prior art. Id. at 8-9. The district court rejected both claims, reasoning that one claim impermissibly narrowed claim 1 in some respect even though it broadened claim 1 in other respects, and that the other claim did not broaden claim 1 at all. Id. at 9. Consequently, the district court vacated the jury verdict of infringement under the DOE. Id. On appeal, the Federal Circuit affirmed.
The Federal Circuit clarified that the ensnarement defense was available for limiting the application of the DOE. Id. at 14 (citing DePuy Spine, Inc. v. Medtronic Sofamor Danek, Inc., 567 F.3d 1314,1322 (Fed. Cir. 2009)). It also clarified that the hypothetical claim analysis conducted by Dr. Jang was not the only method in which a district court can assess whether a DOE theory ensnares the prior art. Id. at 15 n.4. Another method suggested by the Fed. Cir. included determining whether an accused product would have been obvious in view of the prior art. See Conroy v. Reebok Intern., Ltd., 14 F.3d 1570, 1576-77 (Fed. Cir. 1994).
In a hypothetical claim analysis, the patent holder is asked to construct a hypothetical claim that literally covers the accused device, and then prove patentability of the hypothetical claim in view of prior art introduced by the accused infringer. Jang, No. 16-1275 at 15-16 (Fed. Cir. Sep. 29, 2017). The hypothetical claim may slightly broaden an original claim but may not add any narrowing limitations, Id. at 17 (citing Streamfeeder, LLC v. Sure-Feed, Inc., 175 F.3d 974, 983 (Fed. Cir. 1999)),.
In this case, Dr. Jang provided two hypothetical claims: claims three and five. Jang, No. 16-1275 at 8-9, 16-18 (Fed. Cir. Sep. 29, 2017). Hypothetical claim three read:
the first connecting strut intermediate section being non parallel to the first connecting strut proximal and distal sections column configured to provide increased flexibility compared to the first and second expansion columns.
Id. at 16 (strikethrough and emphasis to reflect amendments to claim 1). While the strikethrough broadened claim 1, the italicized words were found to narrow it. Dr. Jang contended that he simply replaced a structural limitation for a functional limitation that encompassed the structural limitation, along with providing other structures that perform that function. Id. at 16-17. Since the hypothetical claim three narrowed claim 1 in some respect, the Fed. Cir. held that it was correct for the district court to reject this claim. Id. at 17.
Hypothetical claim five read:
a first connecting strut including at least a first connecting strut proximal section, a first connecting strut distal section and a first connecting strut intermediate section[.]
Id. at 18 (emphasis to reflect amendment to claim 1). The Fed. Cir. held that this hypothetical claim did not broaden claim 1 at all because the addition of “at least” in this claim was redundant with claim 1’s recitation of “comprising.” Id. Because Dr. Jang failed to submit a proper hypothetical claim, he was unable to meet his burden of proving his DOE theory did not ensnare the prior art. Id. at 19.
One interesting question in this case is why the district court even conducted the post-trial ensnarement hearing after it had decided that BSC owed Dr. Jang royalty payments for past sales as long as the product infringed the ’021 Patent and regardless of its validity, as the jury had already found infringement under the DOE, and the district court had ruled that the assignment agreement made the patentability of the ’021 Patent irrelevant. One possible answer is that if a DOE theory does not pass an ensnarement defense, then there can be no infringement under the DOE, which would mark another area where infringement under DOE is treated less favorably than literal infringement. This would operate to address public policy concerns, as DOE hypothetical claims are not on the face of a patent and hence do not provide notice to the public.
This case once again illustrates how difficult it is for patent holders to win using infringement positions relying on the DOE, considering prosecution history estoppel, the ensnarement hurdle, and the various other rules discussed above. Even though the ensnarement rule analyzes hypothetical claims for patentability like in invalidity challenges, the Fed. Cir. has held that this analysis is a question of law (and thus without a jury requirement) because ensnarement and prosecution history estoppel (PHE) have been historically treated on equal footing, and PHE is a question of law. Jang, No. 16-1275 at 20 (Fed. Cir. Sep. 29, 2017). Further, the hypothetical claim analysis seems to be the preferred method for the ensnarement defense analysis. See Wilson, 904 F.2d at 684 (stating that the hypothetical claim analysis “permits a more precise analysis than determining whether an accused product (which has no claim limitations on which to focus) would have been obvious in view of the prior art.” (emphasis in original)). However, providing a hypothetical claim which broadens an original claim without narrowing it in any way in view of prior art can be very challenging, as demonstrated in Jang. This is particularly true when the prior art has invalidated the original claim in the PTO.
The difficulty of winning infringement under the DOE places a high premium on claim drafting, where claims need to be carefully crafted to cover all disclosed embodiments and all foreseeable variations. Also, during patent prosecution, the differences between the invention and the prior art need to be carefully analyzed so that a patentee does not give up more than is necessary to get the claims allowed. Furthermore, a patentee is reminded that reissue is available within two years after a patent is issued, and allows claims to be broadened in some respects to capture targeted infringing devices while narrowed in other respects to avoid prior art.
l1In 2013, BSC requested an ex parte reexamination of the asserted claims before the PTO, which canceled those claims in 2014. BSC moved for summary judgment using the same tack after the PTO cancelled the asserted claims, but was denied by the District Court for the same reason. See Jang at 6-7.