Police cannot lay criminal charges for drug-impaired driving offences without sufficient evidence. They must have reasonable grounds for stopping drivers, as defined in the Criminal Code, before they can collect this evidence from any driver.
The federal government established three offences for drug impairment, based on the amount of Tetrahydrocannabinol (THC) in a person's bloodstream. THC is the primary psychoactive ingredient in cannabis that impairs a user. One is for having 2 to 5 nanograms (ng) of THC in your blood, and the other is for having 5 ng and above. A third offence is for users who combine 50 mg of alcohol with 2.5 ng of THC in their bloodstream.
If your THC count is so high it falls into one of these offences, the police can charge you. The police must take your THC measurement within two hours of you driving your vehicle.
The police have two methods to detect a drug-impaired driver at the roadside. They are only using one as of now: the Standard Field Sobriety Tests (SFSTs). Tools to test a driver's breath for cannabis exist, but no Canadian police force employs it yet.
Standard field sobriety tests
The police conduct Standard Field Sobriety Tests (SFST) at the roadside if they suspect you are driving while drug-impaired. These tests include:
- The Walk-and-Turn test: walk heel-to-toe in a straight line
- The Horizontal Gaze Nystagmus Test: you must be able to follow a moving object with your eyes smoothly
- The One Leg Stand Test: balance successfully on one leg
If you fail, the police can request you give them an oral fluid sample to test at the roadside. You may refuse to undergo these tests, but you then face criminal charges nearly as serious as drug impairment charges.
Roadside saliva tests
The federal government has approved one saliva testing device for police forces across Canada to use to test for cannabis impairment - the Drager DrugTest 5000. Few police forces have bought the device, let alone employed it. The Drager has not performed well on Canadian research trials. Its problems include:
- Cold sensitivity. The Drager does not work consistently in temperatures below 4 degrees Centigrade. This is a major concern during winter.
- False 'positive' results. The Drager often returns 'false positives', suggesting a person is impaired when they are not. Courts may consider Drager evidence unreliable. If so, they will not convict an accused based on Drager test results alone.
The Drager is undergoing further testing, and the federal government is considering other devices. Police will likely be using the Drager or a similar device in 2019 and beyond. You may refuse to give a saliva sample but will be subject to criminal charges that could be as grave as drug impairment charges.
Testing at the police station
The police can arrest you if you perform poorly on the SFST. You will be taken to the police station and asked to undergo a Drug Recognition Expert Evaluation (DREE). This ten-step process includes:
- Additional sobriety testing
- Measuring your blood pressure, pulse and body temperature
- Measuring pupil size in different lighting conditions
You will be released if the evaluating officer finds no evidence of impairment. But you will be asked for a blood sample if you fail the DREE and the evaluator believes you are drug-impaired.
You need not provide a blood sample unless the police officer has reasonable grounds to suspect that you were driving while drug-impaired. However, you face the same penalty as if you had failed the blood test if you refuse to provide the sample.
A qualified technician must draw the blood sample within two hours after you have been driving. Otherwise, the evidence is inadmissible.
What you should do in this situation
This is a new area of criminal law. Seek legal advice if you have given a saliva sample or a blood sample that will be used to support a drug-impairment charge. The police may have violated your rights if:
- Either sample has been mishandled
- The blood sample was not drawn properly by a qualified technician, or
- Either sample was taken after the two-hour limit
An experienced criminal defence lawyer can determine if a violation has occurred and what can be done to protect your rights.