DUI and DWI are usually defined as driving under the influence or driving while impaired by alcohol or other legal or illegal substances. A DUI law may prohibit driving under the influence of an alcoholic beverage, driving under the influence of a drug, and driving under the combined influence of an alcoholic beverage and any drug (legal or illegal), regardless of blood-alcohol level.
To prove a person is guilty of a DUI offense, the following elements must be proven:
The person operated a vehicle and at the same time was “under the influence” in that his or her ability to drive safely was affected to an appreciable degree by having drunk an alcoholic beverage, taken a drug, or combined alcohol and drugs. Note that everyone’s tolerance is different and some people’s driving can be impaired after having consumed even a relatively small amount of drugs or alcohol.
However, someone with a high tolerance could argue that they weren’t under the influence when charged with a DUI, even though their BAC was at or over .08%.
Example: Cindy Heavyweight left work at 5:00 p.m., and—as she had done every day for the past 20 years—drove straight to the bar. As usual, Cindy had six beers and two shots before setting out for home at 8:00 p.m. While driving home, Cindy was stopped by Officer Smith for a broken taillight. Cindy wasn’t swerving or driving unsafely. When Officer Smith approached Cindy, he could smell a strong odor of alcohol, but Cindy didn’t appear intoxicated. Cindy performed three field sobriety tests perfectly, but a breath test revealed a BAC of.09%. Although Cindy is guilty of driving with a BAC of.08% or higher, she might not be guilty of a DUI based on impairment because there’s no evidence that her drinking affected her driving.
Although some DUI stops (first offenses, for example) are usually treated as misdemeanors, under certain circumstances the crime can be bumped up to a felony, which is far more serious. If a driver kills or injures someone as the result of driving while under the influence of alcohol (or having a BAC of.08% or more in those states that punish this separately), the driver can be found guilty of a felony and could go to state prison for years. Prior convictions for misdemeanor DUI or at-or-over-.08% will usually result in a longer prison sentence.