Inter Partes Reexaminations On The Rise, Becoming Popular Amongst Potential Defendants

The USPTO’s inter partes reexamination procedure has been questioned for its failings, and many potential requesters fear the associated estoppel provisions.* However, a comprehensive analysis of inter partes reexaminations recently updated by Joseph Cohen shows that (1) inter partes reexam filings are clearly on the rise and (2) these reexams are getting good results for the requester (not for the patentee).

The past four one–year periods were analyzed by Cohen, who found that inter partes filings are clearly on the rise:

  • Year Ending: Number of Filings
  • June 30 2002:  4
  • June 30 2003:  18
  • June 30 2004:  26
  • June 30 2005:  52

Results have been strong for the inter partes requester.  In the past four years, 98% of requests for inter partes reexam have been granted and, thus far, only 1% of cases have seen an action that allowed all reexamined claims without change.

* Estoppel: Under Section 315(c) of the Patent Act, a third party that requests inter partes reexamination is estopped from later raising the same issues in a court proceeding. The proposed Patent Act of 2005 would change the estoppel provision and would allow inter partes reexams to apply to all patents (rather than only those filed since 1999). 


  • Joseph Cohen’s paper was published as What’s Really Happening in Inter Partes Reexamination, 87 JPTOS 207 (2005).  An updated version of his paper is available online here.
  • USPTO’s 2004 report to Congress on Inter Partes Reexaminations.
  • Gholz and Pous article on acceptance of Inter Partes Reexams by Patent Attorneys.