What is the test for a motion for a new trial in a sexual assault case?

In upholding the trial court's order granting a motion for new trial, it has been recognized that " 'A court may reject the most positive testimony, though the witness be not discredited by direct testimony impeaching him or contradicting his statement. The inherent probability of a statement may deny it all claims to belief.' [Citation.] The judge has the witnesses before him, and ... 'an equal opportunity with the jury to observe the manner of the witnesses, the character of their testimony, and to judge of their credibility, and to discover their motives; he, too, ought to be satisfied that the evidence as a whole was sufficient to sustain the verdict....' " (People v. Knutte (1896) 111 Cal. 453, 455-456, 44 P. 166; original emphasis.)