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Breathalyzer and roadside tests

Breathalyzer and roadside tests are two ways that police monitor the roads to find drivers who are under the suspicion of operating, or being in care and control of a vehicle, while drunk or under the influence of drugs.


A breathalyzer is an instrument that works by measuring the blood alcohol levels in your blood.

The right for police to stop drivers and for people to be required to provide the police with a breathalyzer test is captured in s. 254 of the Criminal Code of Canada.

That section of the code explains that if a peace officer has reasonable suspicion that a person may be driving or in care and control of a vehicle in the last three hours, while having alcohol or a drug in their body, then section (b) gives the officer the right to demand a breath sample.

If you have been stopped by police and you have refused their request to provide them with a breath sample, you will likely be charged under the Criminal Code with failing to provide a breath sample.

In order for a person, who was either driving or had care and control of the vehicle, to fail a breathalyzer test, he or she must have a blood alcohol content, also known as BAC, in their blood of over 80mg%. That means one has over 80 milligrams of alcohol in their system per one hundred milliliters of blood.

If your breath sample shows a BAC of between 50mg% to 80%mg you are in the “warn” range and would face administrative penalties, such as license suspension.

Roadside test

Just like the Breathalyzer test is sanctioned by section 254 of the Criminal Code, so is a roadside test.

The section that applies to roadside tests is section 254 (a), which states that if the police suspect a person is driving or in care and control of a vehicle while intoxicated, they can require or demand for the person who has been stopped to:

“perform forthwith physical coordination tests prescribed by regulation to enable the peace officer to determine whether a demand may be made under subsection (3) or (3.1) and, if necessary, to accompany the peace officer for that purpose…”

Such tests are also called physical coordination tests or Standardized Field Sobriety tests (SFST). SFST’s can include walking in a straight line back and forth, standing on one leg or following an object with your eyes.

In addition to requiring you to do a roadside Breathalyzer and physical coordination tests, a police officer may also require you to accompany them to a police station for further testing.

If you have been detained, arrested or charged with a drunk driving or an impaired driving offence, contact a lawyer as soon as possible.

Read more:

Criminal Code of Canada s. 254

Alcohol and Drug Impaired Driving


Road Safety in Canada

Know Your Rights

What if the police stop me while I’m driving