Blood Alcohol Concentration (BAC) and Driving Under the Influence

What is Blood Alcohol Concentration (BAC)?

Our clients facing Illinois DUI charges often ask us to explain Blood Alcohol Concentration (often referred to as Blood Alcohol Content or BAC). BAC is most commonly used as a measure of alcohol intoxication for legal purposes.

BAC is usually expressed as a percentage of ethanol in the blood in units of mass of alcohol per volume of blood. For example, a BAC of 0.08 means that there are 0.08 g of alcohol for every deciliter (100 milliliters) of blood.

According to Illinois law, as in most other states, a driver is considered under the influence if he or she has a blood-alcohol content (BAC) of .08 or more. Even though Illinois law sets the legal alcohol level for drivers at .08, a driver can still be charged with and convicted of a DUI when their blood-alcohol content is between .05 and .08, and if there is additional evidence that they were driving while impaired.

How Does Alcohol Affect People Differently?

The two main determinants of how a person is affected by alcohol are the rate at which the alcohol was consumed and the rate at which it was absorbed by the body. The level of a person’s impairment caused by alcohol is also affected by the person’s age, tolerance to alcohol, amount and type of food consumed, as well as their mood and the environment in which they consumed alcohol.

Even small amounts of alcohol consumed may begin affecting a person’s judgment, balance, and coordination. As a result, if a person’s BAC is below the legal limit of .08 their reflexes or reaction times still slow down. Studies have shown that a BAC between .04 and .05 increases the possibility of a driver being involved in an accident. Some studies show that a driver with a BAC of .06 is twice as likely to get into an accident with deadly consequences as a driver who did not consume any alcohol and at a BAC level of .08 they are 11 times more likely to be involved in such an accident.

The only real way to decrease a person’s BAC level is to allow time to elapse without consuming alcohol. On average, it takes human body one hour to metabolize one alcoholic drink – a 12-ounce glass of beer, one 5-ounce glass of wine or 1.5 ounces of hard liquor. Drinking coffee, taking a cold shower or consuming food will not increase sobriety and will not decrease the person’s blood alcohol content.

2018 Illinois DUI Statistics

What do Illinois DUI statistics tell us? According to the Office of the Illinois Secretary of State, the average DUI offender in Illinois is a male (75% of drivers arrested for DUI are male) and 34 years of age (57% arrested are under the age of 35). Most DUI arrests happen on weekends between 11:00 P.M. and 4:00 A.M. and the average BAC of an offender is .16 (twice the legal limit).

Driving Under the Influence of Medical Marijuana (Cannabis)

Unless a driver was lawfully using medical marijuana, a driver is also considered under the influence if they have a Delta-9 THC (the principal psychoactive constituent of marijuana) concentration of 5 or more nanograms per milliliter of blood or 10 or more nanograms per milliliter of other bodily substance within 2 hours of driving, or if they used any other controlled substance or are impaired by medication.

In Illinois, drivers cannot operate motor vehicles if impaired after using marijuana, including prescribed medical cannabis. Since 2015, Illinois became the 20th state to allow the use of marijuana for medical purposes. Authorized patients need to obtain a written certification from a doctor licensed in Illinois and must register with the Illinois Department of Public Health (IDPH) which will issue them a registry ID card.

If a person registers with the IDPH, a note will be placed on their Illinois driving record, which will be available to the police. If that person is stopped by a police officer and the officer has reasons to believe the driver to be impaired by marijuana, the driver will need to undergo a field sobriety testing. A failed field sobriety test or refusal to perform the test will result in a driver’s license suspension.

Additionally, medical marijuana may not be present in a vehicle unless it is stored in a tamper-proof container and placed in an area of the vehicle that is inaccessible while driving, such as the trunk. Driving while impaired by marijuana or driving with an open container may result in the loss of a driver’s license and medical cannabis card.

Contact Illinois DUI Lawyers

If you are charged with DUI, call the DUI defense attorneys at The Davis Law Group, P.C. for a consultation at (847) 390-8500 or get in touch with us via our contact page. Our attorneys have decades of experience representing clients facing DUI charges throughout the Chicagoland area including Cook County, Lake County and DuPage County.