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When Is A Breathalyzer Or Intoxilyzer Test Performed?

The police will make a breath demand when a person is exhibiting obvious signs of impairment. For example, when a person who is flagged over by a R.I.D.E. program is slurring their speech, there is an odour of alcohol on their breath, they are unsteady on their feet and they are driving badly the police will make a breath demand. In this situation, the police would not have to provide him or her with an approved screening device demand. They would likely immediately arrest the person, based upon reasonable and probable grounds that their ability to operate a motor vehicle is impaired by the previous consumption of alcohol.

Upon arrest, the police officer would then read a formal demand (for the “main” or “real” tests) to provide breath samples at the police station. Again, this is a completely different situation from an approved screening device demand. It is not necessary for the police officer to go through the approved screening device demand procedure if they have reasonable and probable grounds that the person is impaired upon observation. Merely exhibiting an odour of alcohol and perhaps bloodshot and glassy eyes would only lead to a “suspicion” that the person had been drinking and had alcohol in their system It would not lead to reasonable and probable grounds that they are impaired or over the legal limit.

To summarize, if a person has fairly obvious symptoms of impairment (as an example, bad driving, slurred speech and an obvious balance problem) the police officer will form reasonable and probable grounds that they are impaired or over the legal limit. The police officer will not give them an approved screening device demand. They will immediately arrest the person and read them a formal breath demand for the ‘real’ breath tests to be taken at the police station. They are then required to provide them with their rights to counsel and allow them to talk to the lawyer of their choosing or duty counsel upon request. Ultimately, two breath samples at least 15 minutes apart (longer with an intoxilyser) will have to be provided at the police station. This two breath samples will have to be taken ‘as soon as practicable’ and the first breath sample must be taken within two hours.


The older machines are called breathalysers/breathalizer. Most larger police departments now use modern computerized approved instruments which are known as “Intoxilyzer.”

If an accused is arrested for impaired driving and/or fails an approved roadside screening device test, the police will then read a breath demand to provide breath samples into either the intoxilizer or breathalizer. The accused will usually be brought to the police station. Breathalyzers or intoxilyzers are prepared by a ‘breath technician’ who has been trained to operate these scientific instruments.

Within a two-hour period of the time of driving or ‘as soon as practicable’, the accused will be required to provide two breath samples into the approved breathalyser. The instrument then analyzes the breath samples and provides an actual blood alcohol reading.

An intoxilyser test/breathalyzer test provides a computerized printout of the time of driving, arrest, demand etc and the actual readings expressed as a percentage. For example, if the computer printout is .123, this means the intoxilyzer analyzed that the person had 123 mg. of alcohol in 100 ml. of blood at the time stated.

It is important to note that the Courts do not consider that these scientific instruments are infallible. This is evidenced by the great success of the Carter defence throughout the province. An accused is not at the mercy of the machine. In fact, a successful Carter defence does not require an accused to ever show where the error lies in the machine. The bottom line is that the Courts have recognized that these instruments are only as good as the operator who uses them and whether they are properly and consistently maintained.


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