Is the exclusion of evidence in a motion alleging improper search justified?

Courts are-and should be-guided by precedents. But the nature of precedents is that a case asserting an improper search and therefore seeking the exclusion of evidence is likely to be, on its facts, just a step from an earlier case in which police behavior was held to be justified and in which the evidence found was admitted. And even though we mouth the rule that any Fourth Amendment exception ought to be "jealously and carefully drawn," Jones v. United States, 357 U.S. 493, 499 (1958), we can't avoid the fact that the defendant before us seeks to exclude evidence that virtually always demonstrates guilt, combined frequently with dangerousness.