Patent Interference

A patent interference was an administrative proceeding before the USPTO's Board of Patent Appeals and Interferences (BPAI) to determine which of two or more competing inventors was the first to invent the same patentable subject matter. Under the pre-AIA first-to-invent system (35 U.S.C. § 135 pre-AIA), priority was awarded to the inventor who first conceived the invention AND who exercised reasonable diligence from just before the other party's conception through the first party's reduction to practice. An interference arose when: two different applications claimed the same or substantially the same invention; or a pending application claimed the same invention as an issued patent (limited to 1 year after patent issue).

In an interference proceeding, priority depended on two key events: CONCEPTION: the complete formulation of a definite and permanent idea of the full and operative invention — the mental part of invention. Conception must be sufficiently definite and complete that a person of ordinary skill could reduce the invention to practice without extensive experimentation. Conception alone is not enough — the inventor must also exercise diligence toward reduction to practice. ACTUAL REDUCTION TO PRACTICE: physically making and testing the invention in its intended environment, confirming it works for its intended purpose. CONSTRUCTIVE REDUCTION TO PRACTICE: filing a patent application that fully describes and enables the claimed invention — filing date serves as constructive reduction to practice date. A party who is second to conceive but first to reduce to practice can win priority by showing the first conceiver did not exercise reasonable diligence from just before the second conceiver's conception through to the first conceiver's actual reduction to practice.

The America Invents Act (AIA), effective March 16, 2013, eliminated patent interference proceedings and replaced them with DERIVATION PROCEEDINGS (35 U.S.C. § 135 AIA). The fundamental change: the U.S. moved from first-to-invent to first-inventor-to-file. Under first-to-file, the first applicant wins — priority contests based on who invented first are largely eliminated. However, derivation proceedings remain for a narrower problem: ensuring the first filer actually invented the claimed invention and did not DERIVE (copy or steal) it from another inventor. Derivation petition: the later-filing inventor petitions the PTAB to show (1) the earlier filer derived the claimed invention from the petitioner (not the other way around); (2) the earlier filer filed without authorization from the inventor. Derivation does not determine who invented first — only whether the earlier filer learned the invention from the petitioner.

Legacy patent interference proceedings: yes, but only in limited circumstances. Interference can still be declared for applications subject to pre-AIA law — applications whose effective filing dates fall BEFORE March 16, 2013. Since continuation applications and national phase applications from pre-AIA PCT applications can still be pending many years after 2013, interference proceedings are still possible but becoming increasingly rare as older applications age out. The PTAB's Patent Trial and Appeal Board handles both legacy interference proceedings (under old rules) and new AIA derivation proceedings (under new rules). An interference can be declared between a pending application and an issued pre-AIA patent within 1 year of the patent's issue.

Priority evidence in an interference proceeding: (1) CONCEPTION EVIDENCE — laboratory notebooks with contemporaneous dated entries; witness testimony corroborating conception (the inventor cannot rely solely on their own testimony — corroboration is required); emails, memos, and design documents dated before the other party's conception; (2) REDUCTION TO PRACTICE EVIDENCE — physical prototypes; test records showing the invention worked; purchase orders for materials; (3) DILIGENCE EVIDENCE — continuous activity from just before the other party's conception through actual or constructive reduction to practice; must explain any gaps in activity; (4) DERIVATION EVIDENCE — (in derivation proceedings) showing the other party learned the conception from the petitioner; evidence of communication between parties. The corroboration requirement was strictly enforced — inventor testimony without corroboration was generally insufficient.