What is the proper test for a witness to be found to have deliberately concealed the truth?

In United States v. Appel (211 F. 495, 496, supra) it was held: "the only proper test is whether on its mere face, and without inquiring collaterally, the testimony is not a bona fide effort to answer the questions at all."

In Matter of Finkel v. McCook (supra) the court stated (p. 63): "There is a distinction between the untruthful statement which does not clearly appear to be such from the face of the record but is uncovered only with the aid of extrinsic evidence and testimony which is so plainly inconsistent, so manifestly contradictory and so conspicuously unbelievable as to make it apparent from the face of the record itself that the witness has deliberately concealed the truth and has given answers which are replies in form only and which, in substance, are as useless as a complete refusal to answer."