In a prior blog entry, we discussed why it is important to conduct a thorough prior art search prior to filing a request for inter partes reexamination.  In short, the statutory language of 35 U.S.C. § 315(c) is intended to limit the third-party requester to a single bite at the invalidity apple.  Any prior art patents and printed publications discovered after the request for reexamination is filed may be excluded as a basis for invalidity in litigation if that prior art was publicly accessible when the request for inter partes reexamination was filed. What if a party is contemplating whether to suggest an interference with a patent or to request inter partes reexamination of the patent?  This may be the case, for example, where the party believes that it has a published application which (i) would sufficiently support at least one claim that would interfere with the targeted claims and (ii) has an earlier effective filing date for that claim than the effective filing date of the targeted claims.  In this scenario, the party’s application qualifies as 35 U.S.C. § 102(e) art against the targeted patent.  Should the party (applicant) conduct a thorough prior art search or merely rely upon its own published application as the basis for the reexamination request?  If a search is to be conducted, when?  And, how thorough should that search be? In order to have an interference declared, an applicant must timely present at least one claim which interferes with one or more claims of the targeted patent.  Typically, a party will present in its application claims “copied” from the targeted patent in order to have interfering claims.  Consequently, any prior art discovered by a prior art search directed to the subject matter of the targeted claims will often be material to examination of the “copied” claims and, pursuant to 37 C.F.R. 1.56, must be disclosed to the PTO.  The disclosed art may delay or, in a worst case, derail an indication of allowability (a prerequisite to an interference being declared).  If the ultimate goal of the party is to obtain its own patent protection for the subject matter claimed in the targeted patent, then the party should forego a prior art search pre-interference.  This reduces the likelihood that the copied claims will be rejected during the examination process.  However, if the party is more concerned with cancelling claims of the targeted patent, then reexamination may be the proper choice.  As discussed above, a thorough prior art search is foundational to the inter partes reexamination vetting process.