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An issued patent I have in mind (patent X, filed in 2003, so subject to 20-year term provisions) says on its face and in its first paragraph that it is a CIP of many patents, but I will just name two of them. Namely, Patent X is said on its face and in its first paragraph to be a CIP of patent Y (filed in 1996) and also a CIP of patent Z (filed in 1994). Patent Y happens to be a CIP of patent Z as well, but there is no specific reference connecting the two.

As it happens, patent Z was not pending the day patent X was filed, but patent Y was pending. Based on the recent Fed. Cir. Medtronic case, the priority claim to patent Z is ineffective, improper, and not able to protect against prior art, because of the lack of copendency of X and Z, notwithstanding that the priority claim could have worked had the applicant established a chain of X to Y to Z.

My question: Given that the priority claim to Z is invalid for lack of copendency (at this point, assume it cannot be fixed by any procedure and know for a fact that it has not been fixed, even after a reexamination), does patent X expire in 2014, or in 2016?

A public policy/notice argument should dictate 2014, but strict reading of 35 USC 120 and 154 likely dictates 2016. If there is case law going either way, I would love to know about it.

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I understand that for purposes of answering the question the assumption is it can't be fixed by any procedure. Since this is a comment, not an answer, couldn't it be fixed in a reissue? The patent is defective and the change would not be broadening. Any claim that was erroneously allowed due to requiring support from Z would need to be canceled. –  George White Aug 24 '14 at 4:29

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