dissenting.
This appeal is from a priority decision in a patent interference proceeding. Although the Board of Patent Appeals and Interferences slipped in its application of the evidentiary rules with respect to corroboration, the Board correctly stated and applied the burdens and standards of *1339proof. I must dissent from my colleagues’ assignment of error to the Board’s statement of the procedural burdens; this court’s departure from decades of precedent and practice is unwarranted.
I
The panel majority treats it as a matter of first impression to set the burdens of proof and of production in patent interferences. These burdens were set long ago; they have been consistently applied by the Patent and Trademark Office; they have often been confirmed by the courts — and they are not as the panel majority announces.
The Board stated its procedural sequence and burdens of proof by quoting from Fisher v. Gardiner, 215 USPQ 620, 625, 1981 WL 48136 (Bd.Pat.Interf.1981):
Inasmuch as Fisher et al. [the junior party] have established a reduction to practice of the subject matter in counts 1, 2 and 4 prior to the senior party’s filing date, the burden shifts to Aymami [the senior party] to prove by a preponderance of the evidence a priority date for that subject matter earlier than the July 12, 1973 date established by Fisher et al. [Emphasis added.]
This is a classical statement of the burdens that apply in a priority contest in the PTO between copending applications: the junior party must go first and present evidence to establish priority of invention, including evidence as appropriate of conception, reduction to practice, and diligence. The burden is on the junior party to overcome the “rebuttable presumption,” set in 37 C.F.R. § 1.657(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.
If the junior party establishes, by a preponderance of the evidence, an invention date that is earlier than the senior party’s effective filing date, the presumption is rebutted. The junior party will then prevail unless the senior party meets its burden of proving an even earlier date of invention.
The panel majority incorrectly holds that the junior party bears the burden of proof at each stage of the proceedings, even after the burden shifts to the senior party. Thus the panel majority errs in holding that “the Board erred in stating that the burden of proof shifted to Brown at any point in this case.” Maj. op. at 1333. The Board did not err. The Board correctly required Brown, the senior party, to meet the burden of proving, by a preponderance of evidence, conception and/or reduction to practice before the date that had been proven by the junior party Barbacid.
The panel majority propounds a new and confusing rule whereby the senior party, in order to defeat the junior party when the junior party has antedated the senior party’s filing date, nonetheless never acquires the burden of proving entitlement to priority. The Board correctly placed on the junior party the burden of rebutting the rebuttable presumption of 37 C.F.R. § 1.657(a). If the junior party cannot do so, the senior party need produce no evidence of its dates of invention. However, when the junior party has established a date of invention earlier than the senior party’s effective filing date, the presumption is rebutted, and the burden then shifts to the senior party to prove its dates by submitting evidence of conception and *1340reduction to practice as appropriate. -See Del Vecchio v. Bowers, 296 U.S. 280, 286-87, 56 S.Ct. 190, 80 L.Ed. 229 (1935) (a presumption is not evidence; it controls the result only when there is a lack of competent evidence).
The senior party’s burden of proof of priority dates is unrelated to the evidence of the junior party’s work. Each party’s showing is based solely on evidence of its own work, and is unrelated to the other party’s proofs; the junior party bears no burden of proof as to the senior party’s dates of conception and reduction to practice. For the senior party to prevail after the PTO’s presumption has been rebutted by the junior party, the senior party must establish its dates in accordance with the same law that applies to the junior party. This procedure remains unchanged from that reported in Greenwood v. Dover, 23 App. D.C. 251, 258 (1904):
Moreover, as Greenwood [the junior party] has been found to have had his conception at least as early as June 20, 1901, the burden is thrown upon Dover [the senior party] to prove a conception prior to that date.
The practice and accompanying burdens were again described in Ellis v. Maddox, 96 F.2d 308, 312, 37 USPQ 520, 523 (CCPA 1938):
In the instant case, Ellis’ [the junior party] earliest claimed date is in February, 1926. If the evidence shows that Maddox [the senior party] completed the invention of the counts prior to this date, it is immaterial what character of proof Ellis submitted to sustain his claim that he completed the invention by February, 1926, since it would follow that the junior party Ellis would not have met the burden imposed upon him.
The current practice is unchanged: see, e.g., English v. Ausnit, 38 USPQ2d 1625, 1630, 1993 WL 835293 (Bd.Pat.App & In-terf.1993):
As for priority, if English [the junior party] proves a date of invention prior to Ausnit’s [the senior party] filing date, the burden shifts to Ausnit to prove an earlier date of invention by a preponderance of the evidence.
Kwon v. Perkins, 6 USPQ2d 1747, 1752 (Bd.Pat.App & Interf.1988) (affd: 886 F.2d 325, 12 USPQ2d 1308 (Fed.Cir.1989)):
Since Kwon [the junior party] has established a date of invention prior to the filing date of Perkins [the senior party], the burden shifts to Perkins to establish an earlier date of invention by a preponderance of the evidence.
Kubota v. Shibuya, 999 F.2d 517, 522, 27 USPQ2d 1418, 1422 (Fed.Cir.1993):
It seems to us that, while the burden initially may be on a party seeking to provoke an interference, or seeking to obtain entitlement to a priority date, once an interference has been declared and a party seeks to change the status of the parties by motion, the burden is then on the movant under the new rules, rather than on the party originally provoking the interference or obtaining entitlement.
These procedures do not conflict with 37 C.F.R. § 1.657(a) and (b), as the panel majority announces. In a definitive text, Charles Gholz summarized the practice in the PTO:
The above rule [§ 1.657] refers only to the burden of a junior party must carry to prove an invention date prior to the senior party’s filing date. A senior party attempting to prove an invention date prior to its own filing date must also prove any such date by the preponder-*1341anee of the evidence. As to facts other than invention dates, the burden of proof is always on the party alleging them, whether that party is the senior or junior party.
Charles L. Gholz, Interference Practice in 6 IRVING KaYTON ET AL, PATENT PRACTICE 24-76 (1989). This practice does not conflict with 37 C.F.R. § 1.657, as the panel majority announces; it implements it, as the PTO interprets and practices its own Rule.1
The Board herein stated the correct procedure and applied the correct standard. I respectfully dissent from the court’s assignment of error to the Board’s statement and application of law and practice.2 A change, if warranted, can only be made by this court en banc.
II
I agree that the Board erred in law in its treatment of the proffered evidence of corroboration. Dr. Reiss’ testimonial and documentary evidence of conception and reduction to practice was supported by witnesses who testified variously that they conducted chemical and biological analyses, ordered and prepared materials, discussed the work in progress and its results, and repeated the work. The purpose of the corroboration requirement is to probe the veracity of the inventor’s assertions by determining, on the entirety of the testimonial and documentary record, whether it is more likely than not that the asserted activities and events occurred. See Price v. Symsek, 988 F.2d 1187, 1195, 26 USPQ2d 1031, 1037 (Fed. Cir.1993) (applying a rule-of-reason analysis in determining whether the inventor’s testimony has been corroborated).
This court’s review is, by statute, “on the record before the Patent and Trademark Office.” 35 U.S.C. § 144. A full record has been presented, of generally undisputed facts. It is our appellate obligation to decide the appeal, an obligation particularly compelling in view of the rapid evolution of technology and the time and resources consumed by the administrative patent process. Applying the correct law to the undisputed facts with respect to conception, diligence, and reduction to practice, it follows that the party Brown established priority of invention before the dates established by the party Barbacid.
. This implementation of PTO rules requires recognition and deference in accordance with the Administrative Procedure Act.
. I take note that the panel majority does not explain how its new rule should affect this interference on remand, leaving the impression that the implications of this change in a century of precedent and practice are neither understood nor considered.