They haven't got no noses,
The fallen sons of Eve;
Even the smell of roses
Is not what they supposes;
But more than mind discloses
And more than men believe.

So laments a dog in G.K. Chesterton's poem The Song of the Quoodle. But even our relatively dull sense of smell can sometimes identify a substance.  In the search and seizure context, it is not unusual for the distinctive smell of marijuana smoke to be a factor in the probable cause determination.  See Monday's Supreme Court decision in Kentucky v. King.

Zoe Tillman reports at BLT that the D.C. Court of Appeals has upheld an open-container conviction based on the officer's sniff, without a lab test.  Other evidence included the defendant's grogginess and disorientation, her bloodshot eyes, and the smell of alcohol on her breath and in her car.  The opinion is here.