Wheetley is a K-9 Officer. He was on a routine patrol with Aldo, a German shepherd trained to detect certain narcotics (methamphetamine, marijuana, cocaine, heroin, and ecstasy). Wheetley pulled over D's truck because it had an expired license plate. Wheetley saw that D was “visibly nervous,” unable to sit still, shaking, and breathing rapidly. Wheetley noticed an open can of beer in the truck's cup holder. D refused to consent to search the truck. Wheetley retrieved Aldo from the patrol car and walked him around the truck for a “free air sniff.” Aldo alerted at the drivers-side door handle. Wheetley concluded he had probable cause to search the truck. His search did not turn up any of the drugs Aldo was trained to detect. But it did reveal 200 loose pseudoephedrine pills, 8,000 matches, a bottle of hydrochloric acid, two containers of antifreeze, and a coffee filter full of iodine crystals--all ingredients for making methamphetamine. D eventually confessed that he routinely “cooked” methamphetamine at his house and could not go “more than a few days without using” it. While out on bail, Ds had another run-in with Wheetley and Aldo. Aldo again sniffed the truck's exterior, and again alerted at the drivers-side door handle. Wheetley once more searched the truck, but on this occasion discovered nothing of interest. D moved to suppress the evidence found in his truck on the ground that Aldo's alert had not given Wheetley probable cause for a search. Wheetley testified about both his and Aldo's extensive training in drug detection. D's attorney focused on Aldo's certification and his performance in the field, particularly the two stops of D's truck. Wheetley conceded that the certification had expired the year before he pulled Ds over. It was also discovered that the State maintained records only of alerts resulting in arrests. The trial court concluded that Wheetley had probable cause and denied the motion to suppress. An intermediate state court summarily affirmed. The Florida Supreme Court reversed. It held that to demonstrate a dog's reliability, the State needed to produce a wider array of evidence. The court particularly stressed the need for “evidence of the dog's performance history.” One dissent indicated that the majority's “elaborate and inflexible evidentiary requirements” went beyond the demands of probable cause. The Supreme Court granted certiorari.