What are the dates to which prior art must adhere, in examination of claims in a continuation-in-part (CIP) nonprovisional patent application?  Each claim in a CIP, whether independent or dependent, has its own priority date.  Each claim in a CIP that is fully supported in the parent application should be examined in comparison with prior art that has a filing date preceding the filing date of the parent application.  Generally, any claims in a CIP that are not supported in the parent application (i.e., which would have been new material and disallowed in a continuation or divisional application) can be examined in comparison with prior art that has a filing date preceding the filing date of the CIP.  This can get messy if there is a long chain of continuations mixed with one or more CIP applications.  Even the parent application itself can be cited as prior art for any CIP claims not supported in the parent (see, e.g., Dennis Crouch, Patentably-O, “Continuations-in-Part (CIPs) and Priority Claims”, September 7, 2012, and “A Higher Written Description Standard for Negative Claim Limitations?”, September 6, 2012, both writing about Santarus v. Par Pharma (Fed. Cir. 2012), brought to my attention by a colleague, Patent Attorney Reg Ratliff).

It is hypothetically possible that a CIP application, during examination, could have an allowed independent claim supported in the parent application, and a dependent claim not supported in the parent application and rejected with art that is newer than the parent application filing date but older than the CIP application filing date.  This would appear to contradict the common (and usually believed inviolable) situation that when an independent claim is allowed, its dependent claims are almost always automatically allowed (e.g., unless they suffer from an objection or some other, non-art related rejection such as under 35 USC §112).  And, the above is the opposite of the occasionally seen rejected independent claim and allowed dependent claim.  Would this seeming paradox be resolved by moving up the independent claim to have the same priority date as the dependent claim, since the independent claim is inclusive of the dependent claim?  But then, two claim sets, one with just that independent claim, and the other with that independent claim (or a slight variation of it) and the dependent claim supported in the CIP but not supported in the parent application would have two different priority dates for the (relatively) same independent claim.  The single independent claim (or one followed by parent-supported dependent claims) would have the priority date of the parent application, and the variation independent claim with the newer dependent claim would have the priority date of the CIP application.  Another paradox.

This curious situation aside, there are some subtleties worth exploring in terms of claim strategy, and which may prove advantageous towards getting claims allowed, which the following genericized examples elucidate.

Suppose the parent application discloses A, B and C, and prior art preceding the filing date of the parent application only shows A and B in combination, but not the combination of A, B and C.  The CIP discloses and claims a method of using A and B, and discloses variation methods for using A and C, and using A, B and C.  During examination of the CIP, prior art preceding the filing date of the CIP is found showing a (similar enough) method of using A and B, which thus anticipates or makes obvious the present claim.  What are some options for amending and arguing the claims?

A method of using A, B and C, if satisfactory to the client and not shown in cited references might be a good choice for an amended claim.  What happens if a reference showing a method of using A, B and C is cited during examination?  Well, if that reference predates the filing date of the parent application, the amended claim is anticipated (and the parent application is likely at risk).  But, if that reference is later than the filing date of the parent application, albeit predating the filing date of the CIP, there may be some room for argument.  True, the method itself is now shown to predate the filing date of the CIP, but the combination of A, B and C is not shown to predate the filing date of the parent application.  One could argue that, since the combination of A, B and C appears in the parent application and is relied on in the amended claim limitations to show novelty supported by the filing date of the parent application, that the amended claim limitations should have the same priority date as the parent application.  A proper rejection of the amended claim would have to show the combination of A, B and C was known prior to the filing date of the parent application.  Success or failure of the argument may depend on the nature of support for the combination in the parent application in comparison to the claim language in the CIP, especially if negative limitations are involved (see Dennis Crouch, op. cit).

An even stronger argument can be made if a rejection of this amended claim combines multiple references, even if some of them predate the filing date of the parent application.  If these references, singly or in combination, do not show the combination of A, B and C is known prior to the filing date of the parent application, especially if some aspect of the motivation cited in the rejection relies on taking a reference that is after the filing date of the parent application, the argument can be made that these references are not properly combined to show A, B and C prior to the filing date of the parent application.

Alternatively, a method of using A and C might be acceptable to the client, and, if not shown in cited references or generally known, might be a worthwhile claim amendment to pursue.  The client might actually be interested primarily in protecting a method of using A, and most competitors would use A and C because B is more expensive or not as reliable, etc., so this would get useful patent protection for the products the client is actually going to make and sell.  These are just examples, and one could develop others with structures and/or methods to explore how prior art and CIP applications interrelate.  This is all part of the art of patenting.