When can a motion for a new trial be denied on the grounds of newly discovered evidence?

In Nebelung v. Norman, 14 Cal.2d 647, at page 655, 96 P.2d 327, at page 331, in denying a motion for a new trial on the ground of newly discovered evidence, the court said: "When a new trial is asked upon the ground of newly discovered evidence, 'the moving party must make a strong case' (Smith v. Schwartz, 14 Cal.App.2d 160, 166, 57 P.2d 1386), and this is particularly true when the alleged newly discovered evidence relates to facts occurring after the conclusion of the tria."