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

"[T]o fall within the exigent circumstances exception to the warrant requirement, an arrest or detention within a home or dwelling must be supported by both probable cause and the existence of exigent circumstances. [Citation.] . . . 'Probable cause exists when the facts known to the arresting officer would persuade someone of "reasonable caution" that the person to be arrested has committed a crime. [Citation.] "[P]robable cause is a fluid conceptturning on the assessment of probabilities in particular factual contexts . . . ." [Citation.] It is incapable of precise definition. [Citation.] "'The substance of all the definitions of probable cause is a reasonable ground for belief of guilt,'" and that belief must be "particularized with respect to the person to be . . . seized."' [Citation.] . . . [] The standard to be applied is an objective one: 'An action is "reasonable" under the Fourth Amendment, regardless of the individual officer's state of mind, "as long as the circumstances, viewed objectively, justify [the] action."' [Citation.]" (People v. Lujano (2014) 229 Cal.App.4th 175, 183 (Lujano).)

Page 5