Two North Georgia troopers say they followed their noses to the 10 pounds of marijuana stashed in the trunk of a car they'd stopped on I-75.

Troopers Jeff Adamson and Kevin Turner said they caught a whiff of "raw marijuana" from within Jarmane Vernon Knox's car. This gave them probable cause to search, find the pot and then arrest Knox and his passenger, Derrick Mikes.

But Knox, of Chattanooga, claims that something about the arrest smells funny. Specially trained dogs are often used to sniff out illicit drugs, but is the human nose that sensitive?

The dispute has spawned a novel challenge in a court motion filed in Gordon County Superior Court. It seeks a court order to have the marijuana put back inside a trash bag and placed in the trunk of a random car in the courthouse parking lot. The troopers would then be given the chance to prove they can really smell as well as they say they can.

The motion, filed Knox's lawyer, David West of Marietta, seeks to have the seized marijuana suppressed as evidence from an unlawful search.

"It's ridiculous and totally stretches the possibilities of scientific fact to suggest these officers could smell a bag of raw marijuana that's tied up and enclosed in the trunk," West said. "They're trying to make us believe they can basically be drug dogs in this case."

District Attorney Joseph Campbell declined to comment on the motion. "We'll certainly review it," he said. "We don't talk about pending cases or pending motions."

Adamson, who is on military leave, could not be reached for comment. Turner did not return phone calls Tuesday seeking comment.

One scientific expert said he believes it was not possible for the troopers to have smelled the pot when standing outside the car.

"They can't do it," said Richard Doty, director of the University of Pennsylvania Medical Center's Smell and Taste Center. "They can't smell it, even if there's a lot of marijuana in the back of the car."

In 2004, Doty co-authored a paper, published in a American Psychology-Law Society journal, that cited a study that found the odor of pot from inside a car trunk was not reliably discernible, even by people with an excellent sense of smell. The study tested five men and five women, using marijuana supplied by the New Jersey attorney general's office that was put in a garbage bag and placed in the trunk of a two-door Chevy.

Little research has been conducted on the human capacity to detect marijuana's odor, the paper added. "This dearth of information bears considerable legal consequence, because courts often accept the argument ... that marijuana's odor can always be detected."

Knox's was arrested Nov. 16, 2006, when he and Mikes were driving north through Gordon County.

In his police report, Adamson wrote, he pulled Knox's car over because its license plate light was out and he could not tell whether the car had a tag.

Adamson said when he walked up to the car, he was overwhelmed by the smell of air fresheners and saw two hanging from the rear view mirror.

Knox, the driver, was instructed to step to the rear of the car. Knox initially gave the officer conflicting information about where he was going, prompting Adamson to walk to the passenger side of the car and talk to Mikes. At the side of the car, Adamson wrote, he smelled "raw marijuana."

Mikes said they had just returned from Greenbriar Mall. But Knox said they had been to the Old National Highway Flea Market.

"Based on my knowledge and training, I felt there was criminal behavior afoot," Adamson wrote.

Adamson then returned to his patrol car to run a check on Knox's driver's license and the car's vehicle identification number.

Adamson also called for backup, summoning Turner to the scene. When Turner arrived, "he clearly smelled raw marijuana coming from within the vehicle."

Knox and Mikes admitted to having earlier smoked a marijuana "blunt" but denied there was any pot in the car, the report said.

The officers searched the car and found the marijuana inside a white trash bag in the trunk.

Gwinnett District Attorney Danny Porter said cases like this are not highly unusual. When he was a drug prosecutor, Porter said, he was involved in cases where he could smell marijuana inside a car.

"These kinds of cases turn on the circumstances of the stop and the credibility of the officers," Porter said. "As for the marijuana, a lot of it depends on how it is packaged and the freshness of it. Sometimes there is a very distinctive odor."

But West, Knox's lawyer, said the court should not take the officers at their word. "I say if these officers really think they are human drug dogs, let's put them to the test," he said.