What is the test for obtaining a warrant for arrest in a criminal case?

There must exist a quantum of information that would "warrant a man of reasonable caution in the belief" that a felony has been committed. Carroll v. United States, 1925, 267 U.S. 132, 162, 45 S.Ct. 280, 69 L.Ed. 443.

A relaxation of the fundamental requirements of probable cause would "leave law-abiding citizens at the mercy of the officers' whim or caprice." Brinegar v. United States, 1949, 338 U.S. 160, 176, 69 S.Ct. 1302, 1311, 93 L.Ed. 1879, reh. den. 338 U.S. 839, 70 S.Ct. 31, 94 L.Ed. 513.

We doubt that the interested officers, on the facts here known to them, could have obtained a warrant from a magistrate for appellants' arrest. Giordenello v. United States, 1958, 357 U.S. 480, 486, 78 S.Ct. 1245, 2 L.Ed.2d 1503.