No recente acórdão Hudson v. Michigan (15-6-2006), a maioria (5-4) entendeu que a violação do «knock and announce» na realização de buscas infringe o IV Aditamento à Constituição mas não implica a proibição de utilizar a prova obtida, existindo outros mecanismos que podem ser utilizados para prevenir a prática pela polícia de tal infracção (em particular disciplinares e cíveis), tendo a opinião vencida sido expressa numa fundamentação ainda mais longa do que a da maioria (a qual aliás teve matizes expressas na declaração do juiz Kennedy). A opinião maioritária do acórdão que pode ser consultado aqui foi assim resumida:
«JUSTICE SCALIA delivered the opinion of the Court with respect toParts I, II, and III, concluding that violation of the "knock-andannounce" rule does not require suppression of evidence found in a search. Pp. 2–13.
(a) Because Michigan has conceded that the entry here was a knock-and-announce violation, the only issue is whether the exclusionary rule is appropriate for such a violation. Pp. 2–3.
(b) This Court has rejected "[i]ndiscriminate application" of the exclusionary rule, United States v. Leon, 468 U. S. 897, 908, holding itapplicable only "where its deterrence benefits outweigh its ‘substantial social costs,’ " Pennsylvania Bd. of Probation and Parole v. Scott, 524 U. S. 357, 363. Exclusion may not be premised on the mere factthat a constitutional violation was a "but-for" cause of obtaining theevidence. The illegal entry here was not the but-for cause, but even ifit were, but-for causation can be too attenuated to justify exclusion. Attenuation can occur not only when the causal connection is remote,but also when suppression would not serve the interest protected bythe constitutional guarantee violated. The interests protected by theknock-and-announce rule include human life and limb (because an
unannounced entry may provoke violence from a surprised resident),property (because citizens presumably would open the door upon anannouncement, whereas a forcible entry may destroy it), and privacy and dignity of the sort that can be offended by a sudden entrance. But the rule has never protected one’s interest in preventing the government from seeing or taking evidence described in a warrant. Since the interests violated here have nothing to do with the seizure of the evidence, the exclusionary rule is inapplicable. Pp. 3–7.
(c) The social costs to be weighed against deterrence are considerable here. In addition to the grave adverse consequence that excluding relevant incriminating evidence always entails—the risk of releasing dangerous criminals—imposing such a massive remedy would generate a constant flood of alleged failures to observe the rule, and claims that any asserted justification for a no-knock entry had inadequate support. Another consequence would be police officers’ refraining from timely entry after knocking and announcing, producing preventable violence against the officers in some cases, and the destruction of evidence in others. Next to these social costs are the deterrence benefits. The value of deterrence depends on the strengthof the incentive to commit the forbidden act. That incentive is minimal here, where ignoring knock-and-announce can realistically beexpected to achieve nothing but the prevention of evidence destruction and avoidance of life-threatening resistance, dangers which suspend the requirement when there is "reasonable suspicion" that theyexist, Richards v. Wisconsin, 520 U. S. 385, 394. Massive deterrence is hardly necessary. Contrary to Hudson’s argument that without suppression there will be no deterrence, many forms of police misconduct are deterred by civil-rights suits, and by the consequences of increasing professionalism of police forces, including a new emphasis on internal police discipline. Pp. 8–13.»
«JUSTICE SCALIA delivered the opinion of the Court with respect toParts I, II, and III, concluding that violation of the "knock-andannounce" rule does not require suppression of evidence found in a search. Pp. 2–13.
(a) Because Michigan has conceded that the entry here was a knock-and-announce violation, the only issue is whether the exclusionary rule is appropriate for such a violation. Pp. 2–3.
(b) This Court has rejected "[i]ndiscriminate application" of the exclusionary rule, United States v. Leon, 468 U. S. 897, 908, holding itapplicable only "where its deterrence benefits outweigh its ‘substantial social costs,’ " Pennsylvania Bd. of Probation and Parole v. Scott, 524 U. S. 357, 363. Exclusion may not be premised on the mere factthat a constitutional violation was a "but-for" cause of obtaining theevidence. The illegal entry here was not the but-for cause, but even ifit were, but-for causation can be too attenuated to justify exclusion. Attenuation can occur not only when the causal connection is remote,but also when suppression would not serve the interest protected bythe constitutional guarantee violated. The interests protected by theknock-and-announce rule include human life and limb (because an
unannounced entry may provoke violence from a surprised resident),property (because citizens presumably would open the door upon anannouncement, whereas a forcible entry may destroy it), and privacy and dignity of the sort that can be offended by a sudden entrance. But the rule has never protected one’s interest in preventing the government from seeing or taking evidence described in a warrant. Since the interests violated here have nothing to do with the seizure of the evidence, the exclusionary rule is inapplicable. Pp. 3–7.
(c) The social costs to be weighed against deterrence are considerable here. In addition to the grave adverse consequence that excluding relevant incriminating evidence always entails—the risk of releasing dangerous criminals—imposing such a massive remedy would generate a constant flood of alleged failures to observe the rule, and claims that any asserted justification for a no-knock entry had inadequate support. Another consequence would be police officers’ refraining from timely entry after knocking and announcing, producing preventable violence against the officers in some cases, and the destruction of evidence in others. Next to these social costs are the deterrence benefits. The value of deterrence depends on the strengthof the incentive to commit the forbidden act. That incentive is minimal here, where ignoring knock-and-announce can realistically beexpected to achieve nothing but the prevention of evidence destruction and avoidance of life-threatening resistance, dangers which suspend the requirement when there is "reasonable suspicion" that theyexist, Richards v. Wisconsin, 520 U. S. 385, 394. Massive deterrence is hardly necessary. Contrary to Hudson’s argument that without suppression there will be no deterrence, many forms of police misconduct are deterred by civil-rights suits, and by the consequences of increasing professionalism of police forces, including a new emphasis on internal police discipline. Pp. 8–13.»
