Some time back, Jacob Sullum made note of the smell experts who defense attorneys have been calling upon to challenge police officers’ claims they could sniff out marijuana inside a person’s house from outside.

Both the police and the smell experts are still at it. The Chicago Tribune takes note of a recent case where police claimed they could smell marijuana that was sealed inside a mason jar, justifying a search:

Last week, a federal judge tossed the evidence — in part because the jar had been destroyed while in police custody. But [Jonathan] Stoffels' defense attorney had also raised an unusual challenge to the second reason for the search, that the officer caught whiffs of marijuana from Stoffels' car.

At a suppression hearing, a taste and smell expert on that skunky, funky weed testified that the odor was unlikely so strong the officer could smell it.

Defense attorneys who have had suspicions about the "strong odor of pot" justification for searches say it's a struggle to challenge the statements, claiming that judges tend to believe the officers and that it's hard to prove a negative.

Reporter Annie Sweeney gives a decent number of inches to James Woodford and Richard L. Doty, the two scientists who have actually researched how odor molecules do their thing :

Woodford is a chemist who specializes in odor molecules and how they can permeate barriers and how a smell dissipates in air. He has been called to testify on the issue numerous times over 20 years, often re-creating scenes to challenge officers' assertions that they could smell marijuana through packages, containers or car trunks. He said evidence in some of those cases was suppressed.

In Stoffels' case, Chicago defense attorney John A. Meyer challenged the officer's right to search the car by relying on the testimony of Richard L. Doty, who treats patients for disorders on taste and smell.

And although there were other problems with the evidence recovered in Stoffels' traffic stop, his defense attorney believes Doty's testimony was key.

"To this case, it was absolutely essential," Meyer said.

The case is a bit more complicated, and Stoffels is hardly out of the woods; he’s facing federal drug manufacturing charges not simple possession. Still, that the judge was skeptical about the officer’s claims is at least something:

[F]or Meyer and other defense attorneys, the ability to challenge the officer's claim with research goes to a broader issue about the Fourth Amendment. Even if illegal contraband is recovered, as it allegedly was in Stoffels' case, a search should be based on legitimate and defensible evidence by the police, they said.

Meyer said he wonders about the countless searches based on suspected marijuana odor in which police never find any contraband.

"People don't complain about it," he said. "This is just a fact of life that you might be stopped and searched. … It matters because the Fourth Amendment protects all individuals against warrantless searches, and once police start abusing that right, everybody is at risk."