Patent Diligence

In the pre-AIA U.S. first-to-invent patent system, diligence refers to an inventor's continuous effort to reduce an invention to practice after conception. When two inventors compete for priority of the same invention — an interference — the general rule is that the first to conceive wins IF that inventor was continuously diligent from just before the competing inventor's conception through the first inventor's own reduction to practice. Without diligence, a later-reducing inventor who conceived second can 'swear behind' (antedate) the first conceiver if the first conceiver was not diligent. Under the AIA (effective March 16, 2013), which adopted a first-inventor-to-file system, diligence is no longer determinative for priority between competing filers — the effective filing date controls. However, diligence remains relevant for: derivation proceedings under the AIA; interference proceedings for applications with pre-AIA effective filing dates; and understanding inventorship in complex historical disputes.

The pre-AIA diligence standard requires CONTINUOUS activity — the inventor must show that from just before the date of the competing inventor's conception through the inventor's own reduction to practice, the inventor worked toward reducing the invention to practice without any unjustified gaps. Key standards: (1) CONTINUOUS ACTIVITY — diligence does not require literally working on the invention every single day; reasonable interruptions for health, financial necessity, or other reasonable causes can be excused; (2) NO UNJUSTIFIED GAPS — significant periods of inactivity not explained by reasonable cause will break the diligence chain; (3) CORROBORATION — diligence must be corroborated by evidence beyond the inventor's own testimony (lab notebooks, purchase orders for materials, engineering records, correspondence); (4) TOWARD THE INVENTION AT ISSUE — activity toward other projects, even valuable ones, does not count as diligence toward reducing the contested invention to practice. GRIFFITH v. KANAMARU (Fed. Cir. 1987): Griffith had earlier conception but lost because he prioritized other research during the period he needed to show diligence — working on a different, administratively more important project was not sufficient justification for delaying reduction of the contested invention to practice.

Griffith v. Kanamaru (Fed. Cir. 1987) is the leading Federal Circuit case on the diligence requirement. FACTS: Griffith (Cornell University) and Kanamaru (Japanese company) both claimed priority to an invention related to aminocarnitine, a compound with potential pharmaceutical applications. Griffith had conceived the invention before Kanamaru filed his patent application in the U.S., but Kanamaru was first to reduce to practice. Griffith argued he was diligent toward reduction to practice during the relevant period. ISSUE: Were Griffith's delays in pursuing reduction to practice during the critical period justified? HELD: Griffith failed to establish the requisite diligence. During the period when Griffith needed to show diligence, he and his graduate student were primarily working on other research projects. The court found that personal preference, administrative convenience, or institutional priorities are not sufficient justification for a significant gap in working toward reduction of the contested invention. SIGNIFICANCE: Griffith establishes that: (1) 'other important work' is generally not a valid excuse for a diligence gap; (2) the diligence requirement is strict — inventors must keep working on the claimed invention during the critical period; (3) institutional research calendars and the preferences of funding agencies do not justify diligence gaps. Griffith lost priority to Kanamaru despite having earlier conception.

While the diligence standard is strict, courts have recognized some valid excuses for gaps in activity: (1) FINANCIAL NECESSITY — the inventor had to work at a paying job or attend to necessary financial obligations that prevented full-time work on the invention; (2) ILLNESS OR HEALTH PROBLEMS — genuine physical or mental health conditions that prevented work; (3) LACK OF MATERIALS — genuine inability to obtain necessary materials, equipment, or expertise, despite good-faith efforts; (4) REASONABLE PROFESSIONAL ASSISTANCE — time spent waiting for response from a professional (e.g., waiting for a patent attorney to draft claims after providing all information); (5) LABORATORY CONSTRAINTS — genuine resource constraints at a research institution, particularly for independent inventors. WHAT IS NOT EXCUSED: prioritizing other research or projects over the contested invention (Griffith); administrative decisions about institutional research priorities; delays for economic or business reasons; failure to pursue available alternatives. CORROBORATION: whatever the excuse, the inventor must corroborate both the gap and the excuse through documentary evidence — oral testimony alone, even from the inventor, is insufficient under the corroboration rule.

Under the AIA (Patent Reform Act of 2011, effective March 16, 2013), the U.S. patent system shifted from first-to-invent to first-inventor-to-file. As a result: PRIORITY under the AIA is determined by the effective filing date of the patent application, not by the dates of conception or reduction to practice. In an AIA derivation proceeding (which replaced interference proceedings), the petitioner must show that the respondent derived the claimed invention from the petitioner — that the petitioner had earlier independent conception and communicated it to the respondent. Diligence between conception and filing is not directly relevant to a derivation proceeding's core question (was the invention derived from the petitioner?), though it can be circumstantially relevant to show originality of conception. RESIDUAL RELEVANCE: (1) Applications with pre-AIA effective filing dates (before March 16, 2013) remain subject to pre-AIA interference rules; (2) Mixed-filing-date interferences (one pre-AIA, one post-AIA application) may involve diligence; (3) Historical patent disputes involving pre-AIA patents can still require analysis of diligence. Bottom line: for new applications filed today, diligence between conception and reduction is not determinative for priority — filing first is all that matters.