In Florida v. Harris, a recent case decided on February 19, 2013, the Supreme Court held that a dog's alert can be sufficient to establish probable cause if all of 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. Justice Kagan quipped, "A sniff is up to snuff when it meets that test."
Police Officer William Wheetley pulled over the defendant because he had an expired license plate. After the defendant did not consent to the search of his truck, Officer Wheetley used Aldo, a German shepherd trained to detect certain narcotics, to conduct a "free air sniff" around the defendant's truck. Aldo alerted Officer Wheetley to the possible presence of narcotics after sniffing the defendant's driver's side door handle. Believing probable cause existed, Officer Wheetley searched the defendant's car without a warrant. Officer Wheetley did not find any drugs in the truck, but he did find many ingredients for making methamphetamine.
The defendant sought to exclude the evidence from the search, arguing that Aldo's alert was not reliable enough to give Officer Wheetley probable cause. The Florida Supreme Court set forth a rigid checklist that the State needed to satisfy in order to show that Aldo's alert was reliable. Relying on Supreme Court precedent rejecting bright-line inquiries toward probable cause, the Supreme Court rejected a strict evidentiary checklist. The Court said that if the State has produced proof from controlled settings that a dog performs reliably in detecting drugs, then probable cause is presumed to exist pursuant to a dog's alert. Of course, a defendant can introduce competing evidence, which the court must then weigh to determine the reliability of a dog's alert.
The Supreme Court found that Aldo's alert was reliable enough to give a police officer probable cause to search the defendant's truck because Aldo passed training courses and his reliability was not undermined.
Michigan's test does not appear to be at odds with the Supreme Court's decision. The Michigan Court of Appeals has said that "a positive reaction by a properly trained narcotics dog can establish probable cause." The Michigan Court of Appeals cited a Sixth Circuit case, which did not use a rigid checklist to determine whether a dog was sufficiently reliable.