What is the test for establishing probable cause when a criminal charge against a defendant is dismissed?

As the court explained in Johnson v. Lewis, supra, 120 Cal.App.4th 443, "'[T]he existence of probable cause is "to be decided in accordance with the circumstances at the time of the detention, unhampered by the outcome of the charge against the plaintiff of the public offense or by the conclusions of the trial court. . . ."' [Citations.] Neither an acquittal nor the dismissal of the criminal charges collaterally estops defendants from asserting the lawfulness of plaintiff's arrest. Accordingly, the dismissal of the criminal charge against plaintiff does not vitiate the validity of her arrest. [Citations.]" (Id. at p. 456, italics added.)