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What Does “BAC” Stand For?

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If you are arrested for driving under the influence (DUI) of alcohol in the Greater Toronto Area, the acronym “BAC” will likely play a leading role in subsequent legal proceedings. While DUI arrests can be based on observations and other evidence of impaired driving, one’s BAC—blood alcohol concentration—serves as the primary evidence used for most Ontario DUI cases. The lack of a BAC reading also serves as evidence to convict suspected impaired drivers charged with failure to provide a breath sample DUI. The penalties for a conviction under that charge are the same for other DUI charges.

Understanding BAC and its Relation to Impairment

BAC is the measurement used to describe how many milligrams (mg) of alcohol are present in every 100 millilitres (mL) of blood. Blood alcohol concentrations can vary because body weight, gender, metabolic rates, contents of the stomach, and other factors that can affect how fast the alcohol enters the bloodstream. However, 0.6 ounces of pure alcohol typically raises someone’s BAC to anywhere from 10 to 30 mg.

That amount of pure alcohol is generally found in:

  • 12 fluid ounces of regular strength beer
  • 8 to 9 ounces of regular strength malt liquor
  • 5 fluid ounces of table wine
  • 1.5 fluid ounces of distilled spirits (rum, whiskey, vodka, etc.)

Rising BAC levels tend to coincide with increased intoxication and impairment. Researchers have tracked the intersection of the three and describe them as followed when applied to an average person:

  • Subliminal Intoxication (BAC between 10 and 50 mg)—As the first stage of intoxication, most people display limited effects, but reaction times may be slightly delayed. Impacts on driving ability include a slight decline in moving target tracking and multitasking.
  • Euphoria (BAC between 30 and 100 mg)—stimulated by the release of endorphins, people feel much more relaxed and confident, but the intoxication starts to impact memory and rational thinking. At 50 mg, object tracking is further reduced, and coordination starts to get impaired. Emergency reaction response timing declines, and some people have difficulty steering. 80 mg causes reduced concentration, speed control wavering, declining information processing, and impaired perception. At 100 mg, the ability to brake properly and maintain position in driving lanes becomes noticeable in many people.
  • Excitement (BAC between 90 and 250 mg)—Depending on the body’s response to and metabolism of the alcohol, this stage of intoxication causes further negative impacts to the senses and motor skills. Effects can include blurred vision, slurred speech, compromised hearing, loss of motor skills, and a significant decline in information processing. The higher BAC levels of this stage often cause noticeable mood swings and potential nausea and vomiting. This stage is also marked by a further and significant deterioration of safe driving ability. The higher BAC levels at this stage usually cause substantial impairment in maintaining vehicle control.
  • Confusion (BAC anywhere between 180 and 300 mg) at some point in this stage, the BAC level of intoxication will begin to impair coordination and short-term memory significantly. Walking may become difficult, and many people lose the ability to recall activities during this time. A person’s ability to safely drive a motor vehicle becomes almost impossible at the higher BAC levels.
  • Coma (BAC above 350 mg)—Most people with a BAC exceeding 350 mg have subdued the natural operation of their respiratory, circulatory, and central nervous systems to the point at which they risk going into a coma. Few people with BACs this high can muster the motor skills needed even to start their vehicles.
  • Death (BAC above 450 mg)—This much alcohol in the system leads to alcohol poisoning and the inability to control and maintain vital functioning. This typically leads to death, which means you can definitely not drive.

BAC and How it Works with DUI Law

For the purposes of DUI law in Ontario, BACs are determined by breath screening devices (breathalyzers) that calculate blood alcohol concentrations by measuring breath alcohol concentrations. Direct blood alcohol concentrations can be derived from blood sampling, which can be conducted by a qualified physician under warrant by a judge if conducting a standard breathalyzer is physically impossible (i.e., because the DUI suspect was injured in a collision and incapacitated at a hospital). Roadside BAC screening used to identify potential impaired drivers does not calculate BAC levels but instead determines whether concentrations are above the warning (50 mg) or legally impaired (80 mg) levels.

Any BAC reading above 80 mg results in a criminal impaired driving charge that is referred to as an over 80 DUI. Readings between 50 and 80 mg BAC can result in administrative warning charges that carry fines and a short license suspension. Subsequent warn offences over the ensuing five years can result in higher fines, longer license suspensions, mandatory attendance in an alcohol education or treatment program, and participation in the ignition interlock program for a third warning offence.

Sections 320.27 (1) to 320.4 (c) of Canada’s Criminal Code lay down exacting requirements for police collection and handling of screening samples, whether through breath or blood. Screening devices must be maintained and operated by a qualified technician whose findings are admissible in court as evidence. Testing must be conducted within two hours of the arresting officer’s initial detainment of the DUI suspect, and individual samples can only be taken at 15-minute intervals.

What Else You Need to Know About BAC and DUIs in Ontario

In Ontario, drivers under age 21, novice drivers of any age (holding G1, G2, M1, or M2 driver’s licenses), and most commercial drivers are subject to the province’s “Zero BAC” rule, which prohibits the presence of any alcohol in the driver’s blood. Drivers charged with Zero BAC offences face harsher administrative and criminal penalties than regular drivers.

The Criminal Code mandates additional fines for over 80 BAC DUIs that involve excessive alcohol blood concentrations. A BAC exceeding 120 mg of alcohol in 100 mL of blood but less than 160 mg of alcohol in 1000 mL of blood raises the minimum fine by at least $500. A BAC that exceedes 160 mg of alcohol in 100 mL of blood increases the minimum fine by at least $1,000. An excessive BAC can also be used as an aggravating factor in assessing other DUI penalties.

If You’re Arrested for DUI in Ontario, Consult with Mass Tsang

Because of the strict legal requirements and significant technical aspects of BAC testing, skilled DUI lawyers often challenge the potential shortcomings of BAC testing and their results. The criminal trial lawyers at Mass Tsang are intimately familiar with all technical and legal aspects of BAC testing. They have mounted numerous successful BAC challenges that have led to withdrawn charges and acquittals. If you or someone you know is facing DUI charges in the Greater Toronto Area, or has a question about BAC results they received in the course of a DUI arrest, the expert lawyers at Mass Tsang today for a free consultation.



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