Gradualism and crisis, always headed the same way, have yielded a constitutional trail of tears catalogued in American state and federal case law. The U.S. Supreme Court hardly noticed the Fourth Amendment until the twentieth century. In the Prohibition-era case Carroll v. U.S. (1925), the Court sanctioned searches of private automobiles on the rather forced analogy of ships at sea. (The next time cops pull you over and search your car, you may blame Chief Justice William Howard Taft.) But the amendment’s core meaning survived awhile longer in areas where it was thought to have always applied.
Meanwhile, emboldened by the Fourteenth Amendment, the Supreme Court undertook to supervise state police practices from the late 1940s on; it would decide if the states were following the Fourth and other amendments. This new project annoyed the states but did little enough for the public. Examining federal search practices in U.S. v. Rabinowitz (1950), the Court declared the word “unreasonable” the key to the Fourth Amendment. Henceforth the Court would philosophize on the “reasonableness” of searches (“in the circumstances”) and periodically announce our ever-waxing-and-waning rights on the accordion model of civil liberties. Warrants pretty much disappeared.
