an interlocutory decree for an injunction and an accounting. 279 Fed. 445. The Circuit Court of Appeals (per Manton, J.) affirmed. 280 Fed 584. In the meanwhile the interference proceedings went on in the Patent Office. On March 31, 1923, the Commissioner of Patents rendered a decision which gave priority to Armstrong. There was an appeal to the Court of Appeals of the District of Columbia, invested at that time with supervisory jurisdiction in the administration of the patent laws. Butterworth v. Hoe, 112 U.S. 50, 60; Postum Cereal Co. v. California Fig Nut Co., 272 U.S. 693. The Court of Appeals reversed the decision of the Commissioner, and decreed priority of invention in favor of De Forest. 54 App.D.C. 391; 298 Fed. 1006. On September 2, 1924, pursuant to the mandate of that court, patents numbers 1,507,016 and 1,507,017 were issued by the Patent Office.

The fight was far from ended. Already there was pending in the District Court in Delaware a suit brought under the authority of R.S. § 4915 (35 U.S.C. § 63') to direct the issuing of a patent to Meissner or his assigns. After the decree in the District of Columbia there was a suit in Pennsylvania under R.S. § 4918 (35 U.S.C. § 66 2),

"Whenever a patent on application is refused, either by the Commissioner of Patents or by the Court of Appeals of the District of Columbia upon appeal from the Commissioner, the applicant may have remedy by bill in equity; and the court having cognizance thereof, on notice to adverse parties and other due proceedings had, may adjudge that such applicant is entitled, according to law, to receive a patent for his invention, as specified in his claim, or for any part thereof, as the facts in the case may appear. . . ."

"Whenever there are interfering patents, any person interested in any one of them, or in the working of the invention claimed under either of them, may have relief against the interfering patentee, and all parties interested under him, by suit in equity against the owners of the interfering patent; and the court, on notice to adverse parties, and other due proceedings had according to the course of equity, may adjudge and declare either of the patents void in whole or in

which was brought by the assignee of the De Forest patents to set aside the Armstrong patent of October, 1914 (No. 1,113,149), all the interested parties being joined as defendants. Later on there was still another suit in Delaware, under R.S. § 4915, to establish priority for Langmuir. The suit in Pennsylvania came to a decree in July, 1926. The decision was in favor of De Forest, 13 F. (2d) 1014, the court adjudging that the holder of the Armstrong patent had failed to overcome the presumption of validity attaching to the De Forest patents under the administrative ruling in the District of Columbia, and that the earlier decision in New York (279 Fed. 445, 280 Fed. 584) did not sustain the defense of res judicata for the reason that the cause had never gone to final judgment. In February and March, 1927, the two suits in Delaware were decided the same way. 18 F. (2d) 338; 18 F. (2d) 345. The decrees in the three suits came up for review before the Circuit Court of Appeals for the Third Circuit. All three were affirmed with a comprehensive opinion by Woolley, J., marshalling the evidence and weighing the competing arguments. As the upshot the court held that the presumption of validity which protected the De Forest patents had not been overthrown, and that apart from any presumption De Forest had made out his title as the original inventor. 21 F. (2d) 918. Writs of certiorari brought the controversy here. 278 U.S. 562. This court affirmed the decree on the authority of Morgan v. Daniels, 153 U.S. 120, and Victor Talking Machine Co. v. Brunswick-Balke-Collender Co., 273 U.S. 670. The first of those cases lays down the rule

part, or inoperative, or invalid in any particular part of the United States, according to the interest of the parties in the patent or the invention patented. But no such judgment or adjudication shall affect the right of any person except the parties to the suit and those deriving title under them subsequent to the rendition of such judgment."

Opinion of the Court.

293 U.S.

that "where the question decided in the Patent Office is one between the contesting parties as to priority of invention, the decision there made must be accepted as controlling upon that question of fact in any subsequent suit between the same parties, unless the contrary is established by testimony which in character and amount carries thorough conviction." 153 U.S. at p. 125. The second case (273 U.S. 670) adds to that presumption of validity the support of the familiar principle, repeatedly applied in our decisions, that the concurrent findings of the courts below will be accepted by this court "unless clear error is shown." See, e.g., United States v. State Investment Co., 264 U.S. 206, 211; Texas & N. O. R. Co. v. Brotherhood of Railway Clerks, 281 U.S. 548, 558; United States v. Commercial Credit Co., 286 U.S. 63, 67.

One might have supposed that controversy would have been stilled after all these years of litigation. It proved to be not so. The petitioners, after repelling every assault from within the ranks of rival claimants, found it necessary to meet a challenge from without. The respondent, Radio Engineering Laboratories, Inc., allying itself with Armstrong, who is paying its expenses, insists that the invention is at large for the reason that De Forest, who received the patents, is not the true inventor, and that Armstrong, who is the inventor, is barred by a final judgment, conclusive between himself and the pretender, from obtaining the patent that is due him, and with it an exclusive right. The evidence in this suit for an infringement is a repetition, word for word, of the evidence in the earlier suits, so far as material to the conflicting claims of Armstrong and De Forest. What has been added is so nearly negligible that to all intents and purposes the records are the same. The District Court (per Campbell, J.) held upon that evidence that the respondent had not succeeded in overcoming the De Forest patents, and entered a decree for the complainants. 1 F.Supp. 65. Upon

appeal to the Court of Appeals for the Second Circuit, the decree was reversed by a divided court with instructions to dismiss the bill. 66 F. (2d) 768. A majority of the court adhered to the conclusion which it had announced eleven years before. 280 Fed. 584. A dissenting opinion enforced the view that De Forest's title as inventor, conclusively established as between himself and Armstrong, should be held, upon substantially the same record, to be good also against others. A writ of certiorari issued from this court. 290 U.S. 624.

The judgments in the suits between Armstrong and De Forest and their respective assignees are not conclusive upon the respondent, a stranger to the record. This is so by force of the accepted limitations of the doctrine of res judicata. It is so by force of the statute (R.S. § 4918), which provides in so many words that “no such judgment or adjudication shall affect the right of any person except the parties to the suit and those deriving title under them subsequent to the rendition of such judgment." But the respondent does not move very far upon the pathway to success by showing that what has been heretofore determined is without conclusive force. A patent regularly issued, and even more obviously a patent issued after a hearing of all the rival claimants, is presumed to be valid until the presumption has been overcome by convincing evidence of error. The force of that presumption has found varying expression in this and other courts. Sometimes it is said that in a suit for infringement, when the defense is a prior invention, "the burden of proof to make good this defense" is "upon the party setting it up," and "every reasonable doubt should be resolved against him." Cantrell v. Wallick, 117 U.S. 689, 695, 696; Coffin v. Ogden, 18 Wall. 120, 124; The Barbed Wire Patent, 143 U.S. 275, 285; Washburn v. Gould, 3 Story 122, 142; H. J. Heinz Co. v. Cohn, 207 Fed. 547, 554; Detroit Motor Appliance Co. v. Burke, 4

F. (2d) 118, 122; Wilson & Willard Mfg. Co. v. Bole, 227 Fed. 607, 609; Stoody Co. v. Mills Alloys, Inc., 67 F. (2d) 807, 809; cf. Morgan v. Daniels, supra, p. 123. Again it is said that "the presumption of the validity of the patent is such that the defense of invention by another must be established by the clearest proof-perhaps beyond reasonable doubt." Austin Machinery Co. v. Buckeye Traction Ditcher Co., 13 F. (2d) 697, 700. The context suggests that in these and like phrases the courts were not defining a standard in terms of scientific accuracy or literal precision, but were offering counsel and suggestion to guide the course of judgment. Through all the verbal variances, however, there runs this common core of thought and truth, that one otherwise an infringer who assails the validity of a patent fair upon its face bears a heavy burden of persuasion, and fails unless his evidence has more than a dubious preponderance. Cf. Philippine Sugar E. D. Co. v. Philippine Islands, 247 U.S. 385, 391. If that is true where the assailant connects himself in some way with the title of the true inventor, it is so a fortiori where he is a stranger to the invention, without claim of title of his own. If it is true where the assailant launches his attack with evidence different, at least in form, from any theretofore produced in opposition to the patent, it is so a bit more clearly where the evidence is even verbally the same. From all this it results that a stranger to a patent suit does not avoid altogether the consequences of a judgment rendered in his absence by establishing his privilege under the doctrine of res judicata to try the issues over again. If he has that opportunity and there is substantial identity of evidence, he may find that the principle of adherence to precedent will bring him out at the end where he would be if he had been barred at the beginning. Cf. National Folding Box & Paper Co. v. American Paper Pail & Box Co., 48