Defending a Drinking and Driving Charge

By Ron Jourard, B.A., M.A., Ll.B.

The most common drinking and driving offence in Canada is Over 80 mgs. Also referred to as Excess Alcohol, this charge is laid if breath or blood tests show that the driver of a motor vehicle (or person in care or control) has a blood alcohol concentration of more than 80 mgs in 100 ml of blood.

(Care or control means being in charge of a motor vehicle. You are presumed to be in care or control if you are sitting – awake or asleep - in the driver’s seat, even if the engine is off.)

Police will demand breath samples

If you were arrested for drinking and driving, either because you blew a fail on a roadside screening device or displayed signs of alcohol impairment, police will demand you to undergo breath tests to determine the amount of alcohol in your blood. Police will take two breath samples; the lower test result is presumed to be your blood alcohol concentration (BAC) at the time of driving (or care or control).

To secure your conviction on a drinking and driving charge involving breath samples, the tests must be conducted with a breath instrument approved for use in Canada such as the Intoxilyzer 5000C, Breathalyzer 900, Breathalyzer 900A or Breathalyzer 900B.

Breath machine deemed virtually infallible

Until recently, Canadian criminal law recognized that machines, and the police officers who operated them, were fallible. Thus, if you satisfied the court that the amount of alcohol in your blood at the time of driving (or care or control) may have been within the legal limit, you were entitled to an acquittal. Thus, unless rejected, evidence that your blood alcohol level did not exceed 80 mg of alcohol in 100 ml of blood raised a reasonable doubt about your guilt.

Under amendments to the Criminal Code, such evidence will no longer suffice. As of July 2, 2008, you will also require evidence that the breath instrument was malfunctioning or operated improperly and that but for the malfunction or improper operation, the readings would have been within the legal limit.

Forensic toxicologist required

To demonstrate at trial that your BAC did not exceed the legal limit you will have to provide evidence about your alcohol consumption. You will also need a forensic toxicologist, an expert on the body's absorption and elimination of alcohol, to calculate your BAC based on the evidence about your alcohol consumption.

If you are charged with a drinking and driving offence in Canada and want to check whether your BAC may have been within the legal limit, use the BAC calculator on this website.

If you have not been tested to determine the rate at which alcohol eliminates from your blood, use a rate of 10 mg per 100 ml of blood per hour. Although your elimination rate is probably faster, it will help to raise a reasonable doubt in court as to your guilt if a calculation based on the slowest rate puts your BAC at the time of the alleged offence within the legal limit. See the Supreme Court of Canada's recent ruling in R. v. Gibson.

Mr. Jourard is a Toronto criminal lawyer specializing in defence of drinking and driving charges. For more information see his website.