§ 1.657 - Burden of proof as to date of invention.

(a) A rebuttable presumption shall exist that, as to each count, the inventors made their invention in the chronological order of their effective filing dates. The burden of proof shall be upon a party who contends otherwise.

(b) In an interference involving copending applications or involving a patent and an application having an effective filing date on or before the date the patent issued, a junior party shall have the burden of establishing priority by a preponderance of the evidence.

(c) In an interference involving an application and a patent and where the effective filing date of the application is after the date the patent issued, a junior party shall have the burden of establishing priority by clear and convincing evidence.