What is the test for evaluating credibility in a motion for a new trial?

This evaluation need not be based on oral testimony. In fact, on a motion for a new trial, a trial court has the discretion to refuse oral testimony altogether. (People v. Ferguson (1932) 124 Cal.App. 221, 229-230.) This is because a new trial is "a reexamination of the issue in the same court, before another jury, after a verdict has been given." ( 1179.) Therefore, for the most part a motion for a new trial will proceed on affidavits submitted by witnesses "by whom [newly discovered] evidence is expected to be given." ( 1181, subd. 8.) However, a court does have the discretion to allow oral testimony, which this court declined to exercise based on its determination that victim's letter lacked credibility.

There have been cases where trial courts have been found to have abused their discretion by declining to hear live testimony during a hearing on a motion for a new trial. For example, in People v. Hairgrove (1971) 18 Cal.App.3d 606, 610, a defendant brought a new trial motion based on a witness' written declaration claiming to be the perpetrator of the crime of which defendant was convicted. At the hearing on the new trial motion, the witness was present in court and willing to testify regarding the contents of his declaration. However, the trial court dissuaded him from testifying and denied the motion for the new trial on the ground that defendant had not shown reasonable diligence in attempting to produce the witness at trial. (Ibid.) The appellate court reversed and remanded for the trial court to hear the witness' testimony prior to ruling on the motion, finding that the court should have taken advantage of "what purported to be critical new evidence." (Ibid.) After hearing the witness' testimony, the trial court would have "all available information before it in ruling on the motion for a new trial." (Id. at p. 611.)