Cite as: 517 U. S. 690 (1996)
Opinion of the Court
way, whether the rule of law as applied to the established facts is or is not violated." Pullman-Standard v. Swint, 456 U. S. 273, 289, n. 19 (1982).
We think independent appellate review of these ultimate
determinations of reasonable suspicion and probable cause is consistent with the position we have taken in past cases. We have never, when reviewing a probable-cause or reasonable-suspicion determination ourselves, expressly deferred to the trial court's determination. See, e. g., Brinegar, supra (rejecting District Court's conclusion that the police lacked probable cause); Alabama v. White, 496 U. S. 325 (1990) (conducting independent review and finding reasonable suspicion). A policy of sweeping deference would permit, "[i]n the absence of any significant difference in the facts," "the Fourth Amendment's incidence [to] tur[n] on whether different trial judges draw general conclusions that the facts are sufficient or insufficient to constitute probable cause." Brinegar, supra, at 171. Such varied results would be inconsistent with the idea of a unitary system of law. This, if a matter-of-course, would be unacceptable.
In addition, the legal rules for probable cause and reasonable suspicion acquire content only through application. Independent review is therefore necessary if appellate courts are to maintain control of, and to clarify, the legal principles. See Miller v. Fenton, 474 U. S. 104, 114 (1985) (where the "relevant legal principle can be given meaning only through its application to the particular circumstances of a case, the Court has been reluctant to give the trier of fact's conclusions presumptive force and, in so doing, strip a federal appellate court of its primary function as an expositor of law").
Finally, de novo review tends to unify precedent and will come closer to providing law enforcement officers with a defined " 'set of rules which, in most instances, makes it possible to reach a correct determination beforehand as to whether an invasion of privacy is justified in the interest of
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