Driving under the Influence in Ontario

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Driving under the influence is the act of driving a motor vehicle with blood levels of alcohol in excess of a legal limit. Similar regulations cover driving or operating certain types of machinery while affected by drinking alcohol or taking other drugs. This is a criminal offense in most countries. Convictions do not necessarily involve actual driving of the vehicle.

In most jurisdictions a measurement such as a blood alcohol content in excess of a defined level, such as 0.05% or 0.08% defines the offense, with no need to prove impairment or being under the influence of alcohol. In some jurisdictions, there is an aggravated category of the offense at e.g. 0.12%. In most countries, anyone who is convicted of injuring or killing someone while under the influence of alcohol or drugs can be heavily fined, as in France, in addition to being given a lengthy prison sentence.

Many states in the U.S.A. have adopted truth in sentencing laws that enforce strict guidelines on sentencing, different from past practice where prison time was reduced or suspended after sentencing had been issued.

The specific criminal offense may be called, depending on the jurisdiction, driving under the influence [of alcohol or other drugs] (DUI), driving under intense influence (DUII), driving while intoxicated (DWI), “operating under the influence” (OUI) operating while intoxicated (OWI), operating a motor vehicle while intoxicated (OMVI), driving under the combined influence of alcohol and/or other drugs, driving under the influence per se or drunk in charge [of a vehicle]. Many such laws apply also to boating, piloting aircraft, or cycling, possibly with different blood alcohol contents than driving. In some jurisdictions there are separate charges depending on the vehicle used, such as BWI (bicycling while intoxicated), which may carry a lighter sentence. In the United States, local law enforcement agencies made 1,467,300 arrests nationwide for driving under the influence of alcohol in 1996, compared to 1.9 million such arrests during the peak year in 1983. In 1997 an estimated 513,200 DWI offenders were in prison or jail, down from 593,000 in 1990 and up from 270,100 in 1986.

In Canada, it is illegal and is punishable under multiple offences in the Criminal Code of Canada, and can also result in various types of driver’s license suspensions. There are a number of powers given to police officer to assist in the enforcement of the offences, and there are a number of presumptions that assist in the prosecution of the offences.

Drinking & Driving – Blood Alcohol Level (BAC)

With the advent of a scientific test for blood alcohol content (BAC), enforcement regimes moved to pinning culpability for the offense to strict liability based on driving while having more than a prescribed amount of blood alcohol, although this does not preclude the simultaneous existence of the older subjective tests. BAC is most conveniently measured as a simple percent of alcohol in the blood by weight. It does not depend on any units of measurement. In Europe it is usually expressed as milligrams of alcohol per 100ml of blood. However, 100ml of blood weighs essentially the same as 100ml of water, which weighs precisely 100g. Thus, for all practical purposes, this is the same as the simple dimensionless BAC measured as a percent. The per mille (promille) measurement, which is equal to ten times the percentage value, is used in Sweden and Finland.

The validity of the testing equipment/methods and mathematical relationships for the measurement of breath and blood alcohol have been criticized. (Taylor 2007)

Driving while consuming alcohol may be illegal within a jurisdiction. In some it is illegal for an open container of an alcoholic beverage to be in the passenger compartment of a motor vehicle or in some specific area of that compartment. In some it may be illegal to be asleep in the driver’s seat of a vehicle without any intention to drive.

The German model serves to reduce the number of accidents by identifying unfit drivers and removing them from traffic until their fitness to drive has been established again. The Medical Psychological Assessment (MPA) works for a prognosis of the fitness for drive in future, has an interdisciplinary basic approach and offers the chance of individual rehabilitation to the offender.

George Smith, a London taxi driver, was the first person to be convicted of drunk driving, on 10 September 1897. He was fined 25 shillings, which is equivalent to £71.33 in 2005 pounds.

Legal limits

Since there is always some amount of alcohol even in non-drinkers’ bodies, they have to have some legal guidelines for determining what behavior is illegal. Often that guideline is something like impairment in driving to any degree that can be shown to be probably caused by recent alcohol consumption.

For purposes of law enforcement, blood alcohol content is used to define intoxication and provides a rough measure of impairment. Although the degree of impairment may vary among individuals with the same blood alcohol content, it can be measured objectively and is therefore legally useful and difficult to contest in court. Most countries disallow operation of motor vehicles and heavy machinery above prescribed levels of blood alcohol content. Operation of boats and aircraft are also regulated.

The alcohol level at which a person is considered to be legally impaired varies by country. The list below gives limits by country. These are typically blood alcohol content limits for the operation of a vehicle. In the United States, the legal limit can vary by state but for all states as of 2011 is 0.08% blood alcohol content as measured by a breath device, urinalysis or blood test. This legal limit is down from 0.15% just a few decades previously.


Zero tolerance

In Canada, it is illegal to have any alcohol in the blood while driving for new drivers undergoing graduated licensing in Ontario, Quebec, Northwest Territories, Manitoba, Alberta, Saskatchewan, British Columbia, Nova Scotia and New Brunswick; drivers under the age of 22 in Ontario


British Columbia, Ontario, Manitoba, Newfoundland, Nova Scotia, New Brunswick—provincial offence


Criminal offence. The Criminal Code of Canada has two distinct offences that directly addresses drinking and driving.

Section 253(1)(a) makes it illegal to operate a motor vehicle or vessel or operate or assist in the operation of an aircraft or railway equipment, or to have care or control of a motor vehicle, vessel, aircraft, or railway equipment, while that person’s ability to operate is impaired by the alcohol, drugs, or a combination of the two (vessel is defined to include “a machine designed to derive support in the atmosphere primarily from reactions against the earth’s surface of air expelled from the machine”).

Section 253(1)(b) makes it illegal to operate a motor vehicle or vessel or operate or assist in the operation of an aircraft or railway equipment, or to have care or control of a motor vehicle, vessel, aircraft, or railway equipment, while that person’s blood alcohol concentration (BAC) is in excess of 0.08% (representing 80 milligrams of alcohol in 100 millilitres of blood).

A person may be charged with one or both of the offences under section 253. Related are “refuse (or fail) to comply” offences.

Test assumptions

Blood alcohol tests assume the individual being tested is average in various ways. For example, on average the ratio of blood alcohol content to breath alcohol content (the partition ratio) is 2100 to 1. In other words, there are 2100 parts of alcohol in the blood for every part in the breath. However, the actual ratio in any given individual can vary from 1300:1 to 3100:1, or even more widely. This ratio varies not only from person to person, but within one person from moment to moment. Thus a person with a true blood alcohol level of .08% but a partition ratio of 1700:1 at the time of testing would have a .10 reading on a Breathalyzer calibrated for the average 2100:1 ratio. A similar assumption is made in urinalysis. When urine is analyzed for alcohol, the assumption is that there are 1.3 parts of alcohol in the urine for every 1 part in the blood, even though the actual ratio can vary greatly.

Breath alcohol testing further assumes that the test is post-absorptive—that is, that the absorption of alcohol in the subject’s body is complete. If the subject is still actively absorbing alcohol, their body has not reached a state of equilibrium where the concentration of alcohol is uniform throughout the body. Most forensic alcohol experts reject test results during this period as the amounts of alcohol in the breath will not accurately reflect a true concentration in the blood.

Field sobriety testing

Historically, guilt was established by observed driving symptoms, such as weaving; administering field sobriety tests, such as a walking a straight line heel-to-toe or standing on one leg for 30 seconds; and the arresting officer’s subjective opinion of impairment. The officer must correctly perform the Field Sobriety Tests (FSTs) that are approved by the National Highway Transportation Safety Administration (NHTSA). The US Department of Transportation explains the Field Sobriety Test as, “a battery of three tests administered and evaluated in a standardized manner to obtain validated indicators of impairment and establish probable cause for arrest.” Starting with the introduction in Norway in 1936 of the world’s first per se law which made it an offense to drive with more than a specified amount of alcohol in the body, objective chemical tests have gradually supplanted the earlier purely judgmental ones. Limits for chemical tests are specific for blood alcohol concentration or concentration of alcohol in breath.


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