What is the test for credibility of a witness?

We defer to the trier of fact's evaluation of credibility. (People v. Snow (2003) 30 Cal.4th 43, 66.) Neither conflicts in the evidence nor "testimony which is subject to justifiable suspicion... justify the reversal of a judgment, for it is the exclusive province of the [trier of fact] to determine the credibility of a witness and the truth or falsity of the facts upon which a determination depends." (People v. Huston (1943) 21 Cal.2d 690, 693, overruled on another point in People v. Burton (1961) 55 Cal.2d 328, 352.) We make an exception only when the witness's statements upon which the trier of fact relied are physically impossible or inherently improbable. "'To be improbable on its face the evidence must assert that something has occurred that it does not seem possible could have occurred under the circumstances disclosed.'" (People v. Mayberry (1975) 15 Cal.3d 143, 150.) The falsity of the statements "'"must be apparent without resorting to inferences or deductions."'" (Ibid.)