Intervening Rights

US Patent Term which refers to when patent claims are amended post-grant, typically in an inter-parties reviewIntervening rights may arise when patent owners/patentees  substitute or amend claims or make arguments to overcome prior art giving rise to estoppels limiting the scope of a patent to be narrower than when granted. 35 U.S.C. § 252 creates two types of intervening rights:

  1. absolute intervening rights which extend only to anything made, purchased, sold, or used “before the grant of the reissue” patent (i.e., products already made at the time of reissue) and might not extend to methods or processes;
  2. equitable intervening rights which do extend to both products and methods and processes and apply after issuance of a reissued patent, provided “substantial preparation was made” in their development “before the grant of the reissue” patent. In particular, equitable rights may protect an accused infringement who deliberately tried to “design-around” an existing patent to have that effort frustrated by new patent claims.

The question of whether intervening rights apply to a given patent is extremely fact intensive and turns on the extent of the changes, if any, to the prior patent claims and how substantial those changes are

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