In Florida v. Clayton Harris (U.S. Supreme Court, 568 U.S. __, February 19, 2013),  K-9 Police Officer William Wheetley of the Liberty County Florida Sheriff's Office pulled over Clayton Harris on June 24, 2006, as part of a routine traffic stop - an expired license plate on his truck - and the officer found the driver to be nervous and saw an open beer can in a cup holder in the vehicle. When Harris declined to permit Wheetley to search his truck, the officer allowed his police narcotics dog Aldo, a German Shepard trained to detect certain narcotics, to sniff the general area and the dog alerted his handler to the possible existence of drugs. Upon that premise, Wheetley believed that he had probable cause to conduct a search of Harris' vehicle and discovered ingredients used in the manufacture of methamphetamine; thereupon, Harris was arrested.

While on bail, as luck would have it, Harris was stopped, this time for a broken brake light, and Aldo, as luck would have it, did another sniff test, issued another alert, but nothing was found in the truck.

Supreme Court Reverses Drunk Driving CaseBill SingerContributor

The key issue here is that Aldo twice issued an alert for the possible existence of drugs. The problem is that no drugs were found. The ingredients discovered in the first stop were not yet in the form of the finished drug. To some degree, Aldo gave a false alarm - twice.

At trial, the court denied a Motion to Suppress but on appeal the Florida Supreme Court reversed, holding that in order to reach the level of probable cause, the State needed to demonstrate the reliability of Aldo through such factors as field-performance records showing how many times the dog had falsely alerted. The absence of such records (as was the fact in this case)  was found to effectively bar any officer in the field from finding probable cause in response to a K-9 dog's sniff test alert for possible narcotics. As such, the Florida Supreme Court found that under the Fourth Amendment, Officer Wheetley lacked probable cause to search Harris' truck.

In reversing the Florida Supreme Court, the United States Supreme Court declined to require officers in the field to maintain field logs of  their dog's hits and misses. The US Supreme Court was satisfied that evidence of a dog's training and proficiency were typically sufficient and that the obligation for a handling officer to have field records for his dog was above and beyond the reasonableness test. In enunciating what would satisfy the predicate "reasonableness," the US court required a flexible, commonsense standard.

In one of the truly more whimsical pronouncements in Supreme Court history, the Court states:

[I]n 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.

III

And here, Aldo's did. The record in this case amply supported the trial court's determination that Aldo's alert gave Wheetley probable cause to search Harris's truck.. . .

Page 9-10 of the Opinion