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Behind the Wheel - Detecting Marihuana Impairment

I recently overheard a conversation between young people where they discussed the daily use of marihuana - on their way to and from school and in their cars. They said it did not affect their ability to drive and that it went undetected by parents, teachers, employers and the police. Could you please discuss what methods are available, if they are being utilized to identify drivers under the influence of marihuana and how effective it is.

I did not receive Drug Recognition Expert (DRE) training during my traffic enforcement service, but I was able to work alongside others who had been trained and learned enough to be confident of my decisions when I issued 24 hour prohibitions for the use of marihuana.

A driver under the influence of marihuana is more difficult to detect than most other illegal drugs, but it does produce the following symptoms: blood shot eyes, accelerated heart rate (tachycardia), muscle tremors and forgetfulness. Marihuana impairments include: difficulties with judgement, depth perception and the ability to maintain attention. All of these skills are necessary for the safe operation of a motor vehicle.

How effective are Drug Recognition Experts? A driver may be convicted of driving while impaired by a drug based on driving or care and control evidence and the impairment evidence given at trial by the DRE. Recent amendments to the Criminal Code have significantly expanded the use of the DRE by making it a requirement for a suspected impaired driver to submit to an exam rather than voluntarily participate.