police officer holding roadside DUI breath testYou might be familiar with a device called a breathalyzer which was used for many years in Canada to determine if drivers were over the legal limit of alcohol in their bloodstream ("legal limit"). Essentially, when the police had reasonable grounds to believe that a person's ability to operate a motor vehicle was impaired by alcohol or where they failed a roadside Alcotest breath test, they would immediately make a breath demand and require them to attend the police station for a breathalyzer test. At the police station, the arrested person would then blow into the breathalyzer's mouthpiece to determine if their blood alcohol concentration ("BAC") was over or under the legal limit. All police services in Canada now use a more modern computerized device called an Intoxilyzer, which uses infrared spectrometry. Most people still refer to approved breath testing instruments as "breathalyzers." In fact, the police in the Greater Toronto Area only use Alcotest devices (i.e., for the initial roadside screening test) and Intoxilyzers to provide BAC evidence in Ontario impaired driving by alcohol cases. While Intoxilyzers are seen as more accurate than the older breathalyzer instruments, they are still fallible.

Read on to learn how these instruments assess BAC and how flaws in the testing procedure or human error can add doubt to a DUI charge in Toronto. It can mean the difference between heavy criminal penalties or having a DUI charge withdrawn by the Crown prosecutor.

How Intoxilyzers Work

With an Alcotest roadside screening breath test, drivers blow into a device at a Toronto DUI stop. The Alcotest device is calibrated to indicate that you have failed the test if you have 100 or more milligrams of alcohol in 100 milliliters of blood. If you fail the Alcotest or other roadside tests, or the police have reasonable grounds to believe your ability to operate a motor vehicle is impaired by alcohol, this allows them to arrest you, make a formal breath demand, and bring you to the police station for further breath testing. At the police station, the police will then demand that you provide two breath samples taken at least 17 minutes apart, into an Intoxilyzer which is an approved breath testing instrument under the Canadian Criminal Code. The test results of breath samples analyzed by an Intoxilyzer are admissible in Canadian criminal courts assuming the police carefully follow a complicated checklist of procedures that are set out in the Criminal Code. The Intoxilzyer 8000C is a common model which is used by police forces across Canada and is designated as an approved instrument for all DUI cases.

The way that alcohol breath testing works with an Intoxilyzer is as follows:

  1. The police will demand you to blow into the instrument. You have no choice in the matter and must provide the breath samples or you will be charged with failure or refusal to comply with a breath demand. The police want a long and continuous breath. This usually means blowing for at least 6 to 10 seconds.
  2. The goal of the police is to ensure that you empty deep lung air from your system. This results in a more accurate reading of the alcohol circulating in your bloodstream.
  3. An Intoxilyzer analyzes breath mostly from the lungs, not the throat or mouth.
  4. The breath sample enters a testing chamber. It is analyzed using infrared spectrometry.
  5. The instrument looks at the actual atoms in the breath sample. As the sample engages with the infrared light, ethanol absorbs the light. Oxygen does not.
  6. The Intoxilyzer compares the predicted proportion of infrared light versus the actual amount reaching the sensor.
  7. Based on this analysis, the Intoxilyzer estimates the amount of alcohol in your system.
  8. The unit of measure is milligrams of alcohol per 100 millilitres of blood. It’s also expressed as a percentage.
  9. The legal BAC limit in Ontario is 0.08mg/100mL. This is equal to a BAC of 0.08%. Another way of expressing this is a person is over the legal limit if they have 80 or more milligrams of alcohol in 100 milliliters of blood. 

In other words, measuring the alcohol content in lung air indirectly measures BAC. The longer and harder you breathe into the Intoxilyzer, the higher the reading should be. This is why officers encourage suspects to blow harder. To obtain Intoxilyzer test results that are admissible in court, the police must obtain two valid breath samples taken more than 17 minutes apart which are in good agreement (i.e., there must be 20 milligrams or less difference between the two breath test readings). In certain situations, the police can demand more than two breath samples to verify the results.

Potential Problems With Intoxilyzer Results

Intoxilyzers are imperfect. Some of this can be due to human error. For example, the breath technician may not know how to set up and test the Intoxilzyer correctly, These types of errors could potentially lead to invalid breath test results. There may also be mistakes made by the police in following various complicated and technical procedures which are set out in the Criminal Code. The following types of mistakes the police may make could be reasons to discount or exclude this evidence in a Greater Toronto DUI defence case:

  • Technical and procedural requirements. There are various complicated technical and procedural requirements that the police must follow to allow the breath test results to be admissible in court, including timing issuesIf there is a breakdown or mistake made by the police in following the proper procedure, your case may get dismissed by a judge or withdrawn by the Crown.
  • Reasonable grounds. Even if the test results are accurate, they could be excluded if the arresting officer did not follow the correct legal standards. Did the officer have reasonable and probable grounds to make a lawful arrest? Subtle cues like bloodshot eyes are not enough.
  • Right to counsel and other Charter issues. You have the right to speak with a lawyer before providing a breath sample at the police station. Were you offered this option and did the police implement your right to counsel properly? A breach of your right to counsel often results in DUI cases being dismissed or withdrawn. 
  • Observation period. The breath technician must watch the driver for at least 15 minutes before the test. This is to look for contaminants such as regurgitated alcohol that could skew results.
  • Technician error. Was the test conducted correctly? If there is any question of a possible mistake, the results may be void.
  • Insufficient maintenance. If the Intoxilyzer is not maintained properly its results may be unreliable. Is the instrument calibrated correctly? Does it pass diagnostic checks? Can you be sure the instrument is not malfunctioning?

Never Plead Guilty Without Talking to a Lawyer

Even if your BAC is under 120, you can still be charged with impaired driving in Toronto. To mount the best defence possible against a possible Ontario DUI charge, you need a skilled and experienced criminal lawyer on your side who can dispute the accuracy of Alcotest and Intoxilyzer test results. Remember that you don’t have to prove you are innocent or were completely sober. The onus is on the Crown to prove your guilt beyond a reasonable doubt. A qualified DUI lawyer can potentially sow those seeds of doubt by questioning the Intoxilyzer testing process.

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