The Legal Effect of a U.S. Patent Claim Referencing Another Patent Claim
Following up my earlier piece on the history of U.S. patent claims referencing other patent claims, I now turn to an important issue regarding the legal effect of a U.S. patent claim referencing one or more other patent claim(s) -- can claims that reference one or more other claims be independent claims (as opposed to the usual dependent claims)? If so, what is the dividing line?
The answer is complicated. A proper dependent claim is a claim that contains 1) “a reference to a claim previously set forth,” and 2) specifies “a further limitation of the subject matter claimed.” 35 USC 112(d). Most claims that reference another claim meet the second criterion, but what about those that don’t? Are they improper dependent claims, or are they independent claims? (Or maybe sometimes one and sometimes the other?) And what if the claims are in different categories (device, method, or composition of matter)?
Must all claims that reference another claim necessarily be dependent claims? In short, no. This is made explicitly clear in PCT and EPO manuals.[1] Both the PCT and EPO manuals give the same three examples for referencing claims that are not dependent claims – 1) an apparatus for carrying out the process of another claim; 2) a process for the manufacture of the product another claim; and 3) a plug for cooperation with the socket of another claim (a claim to one part referring to another cooperating part).[2] These are all considered independent claims. The EPO Guidelines provide a further example: 4) a method for using an apparatus according to another claim.[3] All of these are considered independent claims, and the EPO Guidelines note that claiming an apparatus or a method requires details regarding the apparatus or method, as opposed to merely reciting their connection with (respectively) another process or apparatus.
The MPEP doesn’t ever state expressly that a claim referencing another claim can be an independent claim. What it does say is that a claim for a product made by a process recited in another claim could be a proper dependent claim, but would not be a proper dependent claim if the product could be made by a method other than that of the referenced claim.[4] In another example, the MPEP states that a claim for a method of making a specific product recited in another claim would be a proper dependent claim.[5] (This example corresponds to the PCT/EPO Example 2 of the previous paragraph, with the opposite result – under the PCT/EPO approach a claim like this would be considered an independent claim.)
Just to muddy things up a little more, elsewhere (in the context of indefiniteness) the MPEP okays a claim making a reference to limitations in another claim.[6] It doesn’t take any position there as to whether a claim making a reference to limitations in another claim can be an independent claim, but merely states that examination of dependent claims should be done to make sure they comply with 35 USC 112(d).[7]
Moving beyond the MPEP, in 2007 the USPTO revised 37 CFR 1.75 to state that certain claims that referenced other claims would be treated as independent claims.[8] A claim would have been treated as an independent claim if it referred to another claim but did “not incorporate by reference all of the limitations to which such claim refers,” or if it referred “to a claim of a different statutory class of invention.”[9] In responding to comments on the proposed rule change, the USPTO characterized such claims as “claims in dependent form that are effectively independent claims.”[10]
The treatment in cases of claims referencing other claims is highly dependent on the facts. Ex parte Porter[11] address the situation of a method claim reciting, as its only operational step, utilizing a nozzle recited in another claim. An expanded Board panel reversed an examiner’s contentions that the method claim was an improper dependent claim and also indefinite, opining that the in which the claim “has been an acceptable format for years.” The opinion took no position on whether the claim was independent or dependent, stating that the claim “could be construed as an independent claim,” but noting that the MPEP indicates that such a claim may be a proper dependent claim.[12] In finding the method claim proper, the opinion noted that incorporated by reference all of the subject matter of the referenced claim, and was not broader in any respect than the referenced claim.
In contrast, the Federal Circuit invalidated a claim referencing another claim in Pfizer v. Ranbaxy Labs. [13] The claim in question (claim 6) was a composition claim covering a salt of a compound recited in another composition claim (claim 2), which itself was a dependent claim.[14] Claim 6 had a scope that did not overlap with claim 2. It was assumed by the court to be a dependent claim, but was found to be an improper dependent claim, and thus invalid. It seems that claim 6 could have been treated as an independent claim (and a valid one at that), with the reference to claim 2 just being considered a shorthand reference to the compound recited in that claim.[15]
A year after Pfizer the Federal Circuit considered another issue of claim referencing in Monsanto v. Syngenta Seeds.[16] The process claims in question recited using a product of another (referenced) process claim in one or more further method steps. Monsanto argued the reference should be construed as only a shorthand way of describing the starting material, and that performing the method steps recited in the referencing claims would constitute infringement of those claims. The court ruled instead that the referencing claims were dependent method claims, and that to infringe them would require also performing the steps of the referenced process claim.
What if instead of the reference claim being a process claim, the referenced claim was in product-by-process claim, and the referencing claim recited method steps of using the product of the reference claims to produce something else. That was the situation in Washington Res. Found. v. Sanofi,[17] and the court there extended the holding in Monsanto to find again that the referencing claim was a dependent claim.[18]
Questions regarding claims referencing other claims have also risen on occasion in the last few years in ex parte appeals within the USPTO. In Ex parte Gillis,[19] a claim to a method of medical treatment using devices of four referenced claims (recited in the alternative) was treated as an independent claim.[20] As observed by the Board in Gillis, “the statute does not say that a dependent claim is one that contains a reference to another claim, merely that a dependent claim shall have a reference to another claim.”[21]
And in Ex parte Eisenhardt,[22] a claim reciting a “data storage unit for a system according to claim 1” (with claim 1 not reciting a data storage unit) was treated as an independent claim. The reference to claim 1 was considered merely an intended use for the data storage unit. (The claim was found to be anticipated.)
So where does that leave us? When a claim recites the same category (device, method, or composition of matter) as the claim that it references, and narrows the scope, it is clearly a dependent claim. This appears true even for methods that have steps that might be performed separately, with the product made using one method being used or modified by steps recited in a different, referencing claim. But claims that reference claims in different categories are best treated as independent claims, along the lines of how such claims are treated in the PCT and European rules.
[1] See PCT International Search and Preliminary Examination Guidelines (“PCT Guidelines) 5.19 (“A claim may also contain a reference to another claim even if it is not a dependent claim as defined in Rule 6.4”); EPO Guidelines for Examination (“EPO Guidelines”) F-IV, 3.8 (“A claim containing a reference to another claim is not necessarily a dependent claim as defined in Rule 43(4).”).[2] PCT Guidelines 5.19; EPO Guidelines F-IV, 3.8.[3] EPO Guidelines F-IV, 3.8.[4] MPEP 608.01(n)(III). The Federal Circuit has interpreted a product claim referring to a process of another claim (“The product of the process of Claim 1”) as an independent claim in In re Thorpe, 777 F.2d 695 (Fed. Cir. 1985), finding that the product-by-process claim was anticipated, even though the process in the referent claim was patentable.[5] MPEP 608.01(n)(III). The conclusion here regarding the propriety of a dependent claim seems wrong, but the approach of these two examples is good – the patentability of the method should depend on the details of the method recited in the method claim. This would be the treatment of such a claim if the method claim was written as an independent claim that did not reference another claim.[6] MPEP 2173.05(f).[7] Id. (referencing MPEP 608.01(n)(III)).[8] The rule change was proposed in 2006. Changes to Practice for the Examination of Claims in Patent Applications, 71 FR 61 (Jan. 3, 2006). It was made final in 2007, with an effective date of November 1, 2007. Changes to Practice for Continued Examination Filings, Patent Applications Containing Patentably Indistinct Claims, and Examination of Claims in Patent Applications, 72 FR 46716 (Aug. 21, 2007). Litigation (and a permanent injunction) blocked the implementation of the rule change (part of wide-ranging rule changes which would have seriously impacted prosecution). See Clarification of Patent Regulations Currently in Effect, and Revision in Applicability Date of Provisions Relating to Patent Applications Containing Patentably Indistinct Claims, 73 FR 45999 (Aug. 7, 2008). The USPTO later reversed course, undoing the wide-ranging rule changes (which never took effect). See Changes to Practice for Continued Examination Filings, Patent Applications Containing Patentably Indistinct Claims, and Examination of Claims in Patent Applications, 74 FR 52686 (Oct. 14, 2009). [9] 71 FR at 67.[10] 72 FR at 46724.[11] 25 USPQ2d 1144 (BPAI 1992).[12] Porter cites an MPEP paragraph that remains unchanged in the current MPEP. Compare MPEP 608.01(n), at 600-40 (last paragraph under heading “INFRINGEMENT TEST”) (5th Ed., Rev. 13, Nov. 1989) with MPEP 608.01(n)(III).[13] 457 F.3d 1284 (Fed. Cir. 2006).[14] The independent claim (claim 1) was a composition claim that involved either of two compounds, “or pharmaceutically acceptable salts thereof.” Claim 2 was dependent on claim 1, and specified that it covered one of the compounds. Claim 6 recited a salt “of the compound of claim 2.” Claims 2 and 6 were thus intended to be separate nonoverlapping subsets of what was covered by claim 1.[15] See Tony A. Grasso and Irving N. Feit, “Can a Patent Claim that Refers to Another Claim be Independent? Pfizer v. Ranbaxy Laboratories Reconsidered,” 89 JPTOS 740 (2007).[16] 503 F.3d 1352 (Fed. Cir. 2007). [17] 302 F.Supp.3d 1240 (W.D. Wash. 2018).[18] Note the tension of this ruling with the Federal Circuit’s ruling in Thorpe, supra, note 4, that a claim to a product of a method of a referenced claim is to be treated as an independent claim. Consider if, instead of two claims, the claims in Washington Res. had been recited as a string of three claims:1. A method of making a product.2. The product of the method of claim 1.3. A process of making a further product, using the product of claim 2. According to Thorpe, claim 2 would be an independent claim, but applying Washington Res., claim 3 would be a dependent claim, depending from claim 1. This is illogical. [19] Appeal 2011-007483, Application 11/645,918, 2013 WL 860588 (PTAB Mar. 4, 2013).[20] Or should that be “four independent claims”? We’ll get back to that in a further piece.[21] Id. at 4.[22] Appeal 2012-006236, Application 12/638,347, 2013 WL 4575055 (PTAB Aug. 27, 2013).