Lex the police dog from central Illinois is far from top dog in drug-sniffing skills.

That's the core finding of a potentially influential new ruling from the 7th U.S. Circuit Court of Appeals, which considered the question of how much police should rely on their K-9 partners to justify searches when a dog's own competence, as in Lex's case, is itself suspect.

The opinion stems from an appeal by Larry Bentley Jr, a St. Louis man serving 20 years in prison for drug possession. He argued the 20 kilograms of cocaine Bloomington police found in his car during a 2010 traffic stop derived from an illegal search triggered by Lex.

While the court upheld the conviction, it disparaged Lex and suggested it might have considered tossing Bentley's conviction if police had relied solely on Lex's nose.

"Lex is lucky the Canine Training Institute doesn't calculate class rank," a 15-page opinion said. "If it did, Lex would have been at the bottom of his class."

Lex's trainer at the Bloomington-based dog school staunchly defended the 10-year-old Belgian Malinois on Wednesday, a day after the court's decision.