What is the test for obtaining an opinion of one witness as to the opinion of another?

Undoubtedly the rule thus stated is one of general application and supported by authorities. But we think it has no application to the facts here. Essentially what happened here was not an attempt to procure the opinion of one witness as to the veracity of another witness; what was sought was to point up the contradiction in the appellant's testimony for the purpose of more effectively bringing that contradiction to the attention of appellant and of the jury as part of the cross-examination. When the appellant herself took the stand and undertook to testify upon direct examination concerning these sundry subjects, she subjected herself to cross-examination on behalf of the prosecution as fully as any other witness in the case. Powers v. United States, 223 U.S. 303, 315, 32 S.Ct. 281, 56 L.Ed. 448; Shipley v. United States, 5 Cir., 281 F. 134, certiorari denied 260 U.S. 726, 43 S.Ct. 89, 67 L.Ed. 483.