How Do the Police Prove You are Driving High?

Now that marijuana is legal in Canada, the likelihood of people driving high (or mpaired by marijuana) has risen. Unlike alcohol, however, there is no easy test to determine if someone is legally impaired by marijuana. The Federal Government has approved a device, the Drager DrugTest 5000, that tests saliva to determine the concentration of THC, but there has been concerns raised surrounding this machine to the point both the Ottawa Police Service [link:] and the RCMP [link:].

For police forces that are not investing in the Drager DrugTest 5000, such as OPS has stated that they will not, they will rely on Drug Recognition Experts (DREs). These are officers who are trained to perform a series of tests to determine both (i) whether you are impaired and (ii) if so, by what drug category. This test consists of:

  • a preliminary examination involving pupil measurement and comparison, pulse, eye tracking of an object;
  • a horizontal and vertical “gaze nystagmus test”,
  • a “lack-of-convergence” test;
  • divided-attention tests, which consist of balancing, walking and turning, one legged standing test, finger to nose test
  • blood pressure, temperature and pulse;
  • an examination of pupil sizes under light levels of ambient light, near total darkness and direct light and an examination of the nasal and oral cavities;
  • an examination, which consists of checking the muscle tone and pulse; and,
  • a visual examination of the arms, neck and, if exposed, the legs for evidence of injection sites.

This test performed by the DRE will be the focus of the Crown’s case against you. The opinion of the DRE is the only way that the Crown will be able to prove you were impaired by a drug. It is, therefore, essential to challenge this opinion in Court. This DRE system is relatively new to Canadian law, and with the legalization of marijuana we are likely to see more of these charges, which will bring with it more litigation over the issue.


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