It sounds like you are referring to the old "Aguilar-Spinelli" test, which held that (1) the magistrate had to be be informed of the reasons to support the conclusion that such an informant is reliable and credible, and (2) the magistrate must be informed of some of the underlying circumstances relied on by the person providing the information. The U.S. Supreme Court, in Illinois v. Gates (1983) 462 U.S. 213, abandoned this test in favor of a "totality of the circumstances" test. Under this test the Aguilar-Spinelli factors remain very important to the magistrate's decision to issue the warrant, but the Supreme Court abandoned any
rigid formula. "[The factors] should be understood simply as closely intertwined issues that may usefully illuminate the common sense, practical question whether there is 'probable cause' to believe that contraband or evidence is located in a particular place."
Some states have kept the Aguilar-Spinelli test, because state constitutions may impose stricter standards on searches and seizures than the US Constitution. However, with the adoption of Proposition 8 in 1982, California abolished independent state grounds for excluding evidence, so current U.S. Supreme Court precedent (like Gates) controls. ... Read More