What is the test for probable cause under the Fourth Amendment?

In deciding whether probable cause exists, courts must examine the "totality of the circumstances" at the time of the arrest. (Illinois v. Gates (1983) 462 U.S. 213, 233, [76 L.Ed.2d 527, 545].) "[P]robable cause is a fluid concept turning on the assessment of probabilities in particular factual contexts not readily, or even usefully, reduced to a neat set of legal rules." (Id. at p. 232.) Moreover, a determination of the existence of probable cause turns on an objective analysis of information available to the arresting officer. (Cf. Whren v. United States (1996) 517 U.S. 806, 813 [135 L.Ed.2d 89] ["[s]ubjective intentions play no role in ordinary, probable-cause Fourth Amendment analysis"].)