What is the test for a motion to withdraw a guilty or no contest plea?

The ruling on a motion to withdraw a guilty or no contest plea rests in the sound discretion of the trial court. On appeal, this court must adopt the trial court's factual findings if substantial evidence supports them. Moreover, the reviewing court will sustain the trial court's ruling unless the defendant demonstrates that the trial court exercised its discretion in an arbitrary, capricious, or patently absurd manner, resulting in a manifest miscarriage of justice. (People v. Fairbank (1997) 16 Cal.4th 1223, 1254; People v. Shaw (1998) 64 Cal.App.4th 492, 496.)

In determining whether the statutory grounds are present, the trial court on a contested motion to withdraw a plea of guilty under this section is the exclusive judge of credibility. (People v. Caruso (1959) 174 Cal.App.2d 624, 636.) It is "not bound to accept and give credence to the affidavits submitted in support of the motion" (ibid.) and " 'is not required to accept as true the sworn testimony of a witness, even in the absence of evidence contradicting it, and this rule applies to an affidavit. Further, the trial court as trier of the fact, is the judge of the credibility of the witness whether he testify in person or by affidavit.' [Citations.]" (Ibid.)