Final answer:
The Supreme Court case Illinois v. Gates established the 'totality of circumstances' test for finding probable cause, allowing police to use corroborating evidence to support an informant's tip.
Step-by-step explanation:
The Supreme Court case you're referring to is Illinois v. Gates, which established the "totality of circumstances" test in finding probable cause under the Fourth Amendment. This 1983 decision signaled a shift from the strict two-pronged test of an informant's veracity and basis of knowledge to a more flexible assessment that considers the overall reliability of a tip. If police can provide corroborating evidence to support an informant's information that initially fails these prongs, it may still pass under the totality of the circumstances approach. This case emphasizes that corroborating evidence bolstering an informant's tip can help establish the probable cause necessary for obtaining a warrant or taking action.