What is the legal test for determining probable cause for a search warrant?

,7] There is nothing inherent in the process of determining probable cause that renders it beyond the capacity of lay persons to resolve. our legal system has long entrusted nonlawyers to evaluate the legal significance of complex, factual data. For example, grand jurors determine probable cause to indict and trial jurors determine whether guilt is proved beyond a reasonable doubt. (Shadwick v. City of Tampa (1972) 407 U.S. 345, 351--352, 92 S.Ct. 2119, 2123--2124, 32 L.Ed.2d 783, 789.) Each of these functions is at least as important as the determination of probable cause to issue a search warrant.