There's apparently a breathalyzer in development[0] that can detect use within the past two hours. [0] http://www.ctvnews.ca/canada/thc-breathalyzer-could-help

There's apparently a breathalyzer in development[0] that can detect use within the past two hours. [0] http://www.ctvnews.ca/canada/thc-breathalyzer-could-help-police-detect-stoned-drivers-1.1927203 http://www.ctvnews.ca/canada/thc-breathalyzer-could-help-pol...