Police officers following a suspect into an apartment complex in Lexington, Ky., don’t know which apartment their man has entered. But wafting through one of the closed apartment doors is the familiar odor of marijuana. The smell provides reason to believe criminal activity is afoot, probable cause for a warrant to search the apartment.

Arrest, Detention and the G20: There is More to Civil Liberties than Freedom From Arrest           Statement by Ombudsman André Marin   December 9, 2010