In what circumstances will the discovery of evidence of criminal activity post-arrest not be used as justification for a search warrant?

Improper police activities will occasionally lead to discovery of probative inculpatory evidence of crime, as happened here. But we have long recognized that such post-arrest discoveries of evidence may not be invoked to justify unconstitutional police activity. See Wong Sun v. United States, supra, 371 U.S. at 484, 83 S.Ct. at 415 ("That result would have the same essential vice as a proposition we have consistently rejected that a search unlawful at its inception may be validated by what it turns up"). By deterring police misconduct, this rule serves to guard the innocent against unwarranted police intrusion as well.