JUSTICE KAGAN delivered the opinion of the unanimous Court.
In this case, we consider how a court should determine if the “alert” of a drug-detection dog during a traffic stop provides probable cause to search a vehicle. The Florida Supreme Court held that the State must in every case present an exhaustive set of records, including a log of the dog’s performance in the field, to establish the dog’s reliability. See 71 So. 3d 756, 775 (2011). We think that demand inconsistent with the “flexible, common-sense standard” of probable cause. Illinois v. Gates, 462 U. S. 213, 239 (1983).
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. . . The test for probable cause is not reducible to “precise definition or quantification.” Maryland v. Pringle, 540 U. S. 366, 371 (2003). “Finely tuned standards such as proof beyond a reasonable doubt or by a preponderance of the evidence . . . have no place in the [probable-cause] decision.” Gates, 462 U. S., at 235. All we have required is the kind of “fair probability” on which “reasonable and prudent [people,] not legal technicians, act.” Id., at 238, 231 (internal quotation marks omitted).
In evaluating whether the State has met this practical and common-sensical standard, we have consistently looked to the totality of the circumstances. . . . .
The Florida Supreme Court flouted this established approach to determining probable cause. To assess the reliability of a drug-detection dog, the court created a strict evidentiary checklist, whose every item the State must tick off. [Footnote omitted.] Most prominently, an alert cannot establish probable cause under the Florida court’s decision unless the State introduces comprehensive documentation of the dog’s prior “hits” and “misses” in the field. . . . .
Making matters worse, the decision below treats records of a dog’s field performance as the gold standard in evidence, when in most cases they have relatively limited import. Errors may abound in such records. If a dog on patrol fails to alert to a car containing drugs, the mistake usually will go undetected because the officer will not initiate a search. Field data thus may not capture a dog’s false negatives. Conversely (and more relevant here), if the dog alerts to a car in which the officer finds no narcotics, the dog may not have made a mistake at all. The dog may have detected substances that were too well hidden or present in quantities too small for the officer to locate. Or the dog may have smelled the residual odor of drugs previously in the vehicle or on the driver’s person. [Footnote omitted.] Field data thus may markedly overstate a dog’s real false positives. By contrast, those inaccuracies—in either direction—do not taint records of a dog’s performance in standard training and certification settings. There, the designers of an assessment know where drugs are hidden and where they are not—and so where a dog should alert and where he should not. The better measure of a dog’s reliability thus comes away from the field, in controlled testing environments. [Footnote omitted.]
For that reason, evidence of a dog’s satisfactory performance in a certification or training program can itself provide sufficient reason to trust his alert. If a bona fide organization has certified a dog after testing his reliability in a controlled setting, a court can presume (subject to any conflicting evidence offered) that the dog’s alert provides probable cause to search. The same is true, even in the absence of formal certification, if the dog has recently and successfully completed a training program that evaluated his proficiency in locating drugs. . . . .
A defendant, however, must have an opportunity to challenge such evidence of a dog’s reliability, whether by cross-examining the testifying officer or by introducing his own fact or expert witnesses. The defendant, for example, may contest the adequacy of a certification or training program, perhaps asserting that its standards are too lax or its methods faulty. So too, the defendant may examine how the dog (or handler) performed in the assessments made in those settings. . . . .
In short, a probable-cause hearing focusing on a dog’s alert should proceed much like any other. The court should allow the parties to make their best case, consistent with the usual rules of criminal procedure. And the court should then evaluate the proffered evidence to decide what all the circumstances demonstrate. If the State has produced proof from controlled settings that a dog performs reliably in detecting drugs, and the defendant has not contested that showing, then the court should find probable cause. If, in contrast, the defendant has challenged the State’s case (by disputing the reliability of the dog overall or of a particular alert), then the court should weigh the competing evidence. In all events, the court should not prescribe, as the Florida Supreme Court did, an inflexible set of evidentiary requirements. The question—similar to every inquiry into probable cause—is whether all the facts surrounding a dog’s alert, viewed through the lens of common sense, would make a reasonably prudent person think that a search would reveal contraband or evidence of a crime. A sniff is up to snuff when it meets that test.