Written Description Inapplicable to Doctrine of Equivalents

The written description requirement does not extend to equivalents asserted under the doctrine of equivalents, according to a recent order in the District of Delaware. The district judge in Sprint v. Cox resolved dueling summary judgment motions to find the patents not invalid.

The case began with Sprint suing Cox over three related patents about broadband telecommunications (among other patents), U.S. Patent Nos. 6,473,429; 6,343,084; and 6,298,064. The court construed the asserted claims as only covering “connection-oriented” technology, such as Asynchronous Transfer Mode (ATM). Because Cox only used internet protocol (IP), which the claim construction excluded, the court found that Cox did not literally infringe the patents. Accordingly, Sprint revised its infringement theory to rely on the doctrine of equivalents.

In this motion, Cox again pushed the distinction between ATM and IP. According to Cox, by accusing IP systems under the doctrine of equivalents, Sprint was effectively broadening the scope of the claims beyond what the common specification of the patents could support, implicating the written description requirement of 35 U.S.C. § 112 ¶ 1.

But this time, Cox ran out of luck. The court ruled for Sprint, noting multiple problems with Cox’s argument. To begin with, the court interpreted Cox’s arguments as attempting to broaden the earlier claim construction ruling limiting the claims to ATM—even though Cox already won that argument. Moreover, the new claim construction arguments were based on the accused product. As is blackletter patent law, the claims must be “construed without reference to the accused device.”

Besides relitigating claim construction, Cox also relied on doctrines having to do with infringement, not validity. First, Cox used the doctrine of vitiation, which applies when “the accused device contain[s] the antithesis of the claimed structure.” If vitiation applies, then the accused product is not an equivalent, meaning no infringement. Second, Cox relied heavily on a case about ensnarement. Ensnarement prevents a patent from having an equivalent that would “ensnare” the prior art, which, again, would mean no infringement. Finally, Cox relies on a case about the dedication-disclosure doctrine, which states that when a patent states but does not claim subject matter, that subject matter is dedicated to the public. The consequence, again, is noninfringement.

With Cox left without a leg to stand on, the court granted summary judgment of no invalidity for lack of written description.

Lessons for Practice

Even though Cox’s execution came off as muddled, their intuition seems right. Sprint’s patents were about ATM, and Cox’s products used IP, something quite different. As the court noted, had Cox reformulated the arguments as against infringement rather than validity, they would have had a better chance of success.

Cox may have had good reasons for not doing so. Ensnarement, for example, requires a piece of prior art to be ensnared, and Cox may have been unable to find one. And for vitiation, the timeframe evaluating whether an accused product is antithetical to the claim limitations is the time of infringement, not the time of invention. Perhaps ATM and IP are no longer so antithetical as they were when the patents were applied for in 1995.

This case demonstrates the value of thinking a few moves ahead in litigation. Infringement or noninfringement positions often motivate proposed claim constructions; such positions should consider the doctrine of equivalents as well as literal infringement. Creative understandings of doctrine may not be able to save you later on.

Upcoming Webinar

Functional Claiming After Williamson v. Citrix
December 14, 2017 at 12:00 pm CST
During the webinar, Charles Bieneman will cover strategies for avoiding – or embracing – functional claim interpretations, and for avoiding findings that functional claim language is indefinite. Register

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