Edward Ryan

Conditional language seems like a natural choice for describing computer-based inventions. The if-then structure mimics computer logic, allowing an algorithm to be translated directly into the claims. But, thanks to a counter-intuitive and inconsistently applied principle of claim interpretation, using this language can result in claim elements being ignored entirely–both in prosecution and in litigation.

How are conditional claim limitations interpreted?

Conditional (or “contingent”) claim limitations recite a step or function that is only performed upon the satisfaction of some condition. In a method claim, a conditional limitation might follow the structure, “if A, then B,” reciting that the step B is performed if the condition A occurs. An example might read, “turning on the air conditioner if the temperature exceeds a threshold.” Other conditional language can include, “when,” and, “until.” In this example, there could be many situations in which that air conditioner turns on, but the claim affirmatively recites that the air conditioner definitely turns on when the temperature is above the threshold.

The intuitive approach is to read conditional claim language for its plain meaning, stating a process that could perform differently in different circumstances. However, the courts and the PTAB have interpreted such language differently. The key question that they address is, “How should the limitation be interpreted if the condition is never met?” Following the above example, what does the air conditioner do if the temperature never reaches the threshold?

The most-cited case on this point is Ex parte Schulhauser, PTAB Appeal No. 2013-007847 (2016). Additional information can be found in MPEP §2111.04(II). The PTAB found, “If the condition for performing a contingent step is not satisfied, the performance recited by the step need not be carried out in order for the claimed method to be performed.” Schulhauser at 10. As a result, if there is a possibility that the condition is not met, then the Examiner need not find prior art addressing the corresponding element. When the claim recites two possibilities for a condition (i.e., A and not-A), then the Examiner will only have to find one of the possibilities in the prior art.

This holds true in litigation as well. See Cybersettle v. Nat’l., 243 Fed. Appx. 603, 607 (Fed. Cir. 2007). A conditional limitation need not be met to find infringement, but also is not needed to establish invalidity. As a result, patents with conditional limitations may have surprisingly broad scope, resulting in unexpected exposure to validity challenges.

Different treatment in method and system claims

Notably, the above analysis only applies to method claims. In Schulhauser, the PTAB found that the means-plus-function limitations of the system claims, which recited conditional performance of a function, should nonetheless be considered. See Schulhauser at 14. The PTAB held:

The broadest reasonable interpretation of a system claim having structure that performs a function, which only needs to occur if a condition precedent is met, still requires structure for performing the function should the condition occur. This interpretation of the system claim differs from the method claim because the structure (i.e., a processor programmed to perform an algorithm for carrying out the recited function should the recited condition be met) is present in the system regardless of whether the condition is met and the function is actually performed.

See id (emphasis added).

As a result, claims directed to a method are interpreted differently than claims directed to a system that performs that method. See id.

An evolving standard

The PTAB has continued to issue decisions that address the question of conditional limitations. In the recent Ex parte Gopalan decision, the PTAB addressed a claim where all of the features were recited in a conditional manner. A first step of “identifying … an outlier” was performed if “traffic is outside of a prediction interval.” A second step of “identifying” was performed “only when a count of outliers … is greater than or equal to two, and exceeds an anomaly threshold.” These were the only two elements of the independent claim. Thus, if the traffic is never outside Gopalan’s prediction interval, then the steps of the method are never performed.

However, the PTAB distinguished Schulhauser and noted that this construction “would render the entire claim meaningless.” Gopalan at p. 5. The Board went on to state, “Although each of these steps is conditional, they are integrated into one method or path and do not cause the claim to diverge into two methods or paths, as in Schulhauser. Thus, we conclude that the broadest reasonable interpretation of claim 1 requires the performance of both steps…” Id. at p. 6.

The decision in Gopalan was not unanimous and included a strong dissent. The dissenting judge pointed out that Schulhauser does indeed control the interpretation of claims with only a single conditional branch and, further, that the question of whether a claim is rendered “meaningless” appears to be one of definiteness, rather than obviousness. Furthermore, the dissent points out that there were dependent claims that recited non-conditional features, and that the majority failed to consider how those features would affect their holding. The conflict seems to be ripe for resolution by the Federal Circuit.

The path forward

In view of the inconsistent application of this caselaw by patent examiners, it falls to the practitioner to take care in claim drafting. The law is clear that conditional language is acceptable in apparatus claims and is interpreted as reciting a structure that is designed to perform any of the recited conditional functions in the appropriate circumstances. When drafting method claims, however, the true scope of the claim depends on the broadest branch. Thus, unless both branches recite a novel, non-obvious feature, the best course of action seems to be to avoid conditional language altogether.

To accomplish this, a practitioner should select the most important branch and recite each step as being inevitable, avoiding such trigger words as, “if,” “when,” and, “until.” To follow the example given above, the conditional language of “turning on the air conditioner if the temperature exceeds a threshold,” becomes simply, “turning on the air conditioner,” or, “turning on the air conditioner based on the temperature.” If another branch of the logic is also regarded as being significant and independently patentable, then a second independent claim that follows the second branch would be a safe solution.

It is unclear how this principle will develop as the Board and the Federal Circuit continue to consider different types of conditional features. For the time being though, it is worthwhile to proactively strip conditional language from claims to protect them from adverse interpretations in litigation.