What is the test for determining whether a witness's testimony is "unbelievable"?

"Unless the appellate court can say that the testimony is so obviously and inherently improbable as to leave the court no recourse without self-stultification, except to reverse the judgment, the reviewing court should not interfere with the verdict and the judgment of the trial court upon that ground. [Citation.] Such improbability must 'plainly appear before the reviewing court should assume the functions of the [trier of fact].' [Citation.] 'Contradictions and inconsistencies in the testimony of a witness alone will not constitute inherent improbability' [citation], and 'it is not sufficient that the testimony may disclose circumstances which are unusual' [citation]." (People v. Moreno (1938) 26 Cal.App.2d 334, 336-37.) The improbability in the testimony must be intrinsic and its falsity apparent on its face without resort to comparison with other evidence. (People v. Ennis (2010) 190 Cal.App.4th 721, 729 [appellate court may reject testimony only when it is "'"'unbelievable per se, physically impossible or wholly unacceptable to reasonable minds'"'"].)

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