Does the fact that a witness testified untruthfully at a previous trial constitute a finding that he is testifying perjuriously at trial?

The fact that a witness testified untruthfully at a prior time does not require a finding that he is testifying perjuriously at trial. United States v. Margolis, 3 Cir., 1943, 138 F.2d 1002, 1004. It is for the jury to say whether his testimony at trial is truthful, in whole or in part, in the light of the witness' demeanor, his explanations and all the evidence in the case. United States v. Reina, 2 Cir., 242 F.2d 302, 307, certiorari denied 1957, 354 U.S. 913, 77 S.Ct. 1294, 1 L.Ed.2d 1427; United States v. Lennon, 2 Cir., 246 F.2d 24, 28, certiorari denied 1957, 355 U.S. 836, 78 S.Ct. 60, 2 L.Ed.2d 48.