Legal Definitions - driving under the influence (DUI)

DUI stands for Driving Under the Influence. It is a serious criminal offense that occurs when a person operates a motor vehicle while their ability to drive safely is impaired by alcohol, illegal drugs, or even legally prescribed medications or over-the-counter drugs.

The core principle of a DUI charge is that the driver's mental or physical faculties are compromised to a degree that makes them unsafe behind the wheel. While many DUI cases involve a driver's blood alcohol content (BAC) being at or above the legal limit (often 0.08% for adults), a person can also be charged with DUI if they are impaired by other substances, or if their BAC is lower but their driving is clearly affected. Law enforcement officers can detect impairment through observation of erratic driving, field sobriety tests, and chemical tests of breath, blood, or urine. Refusing these chemical tests often carries its own penalties, such as automatic license suspension, due to implied consent laws.

• Scenario: After attending a friend's birthday celebration where he consumed several alcoholic beverages over a few hours, Mark decides to drive home. On the way, a police officer observes his car swerving slightly between lanes and driving inconsistently below the speed limit. The officer pulls Mark over, notices signs of alcohol consumption, and Mark subsequently fails a field sobriety test and a breathalyzer test, showing a BAC above the legal limit.
  Explanation: This illustrates a classic DUI scenario where Mark's judgment and motor skills were impaired by alcohol, leading to unsafe driving behavior and a confirmed BAC over the legal limit, resulting in a charge of Driving Under the Influence.
• Scenario: Sarah recently started a new prescription medication for anxiety, which her doctor warned could cause drowsiness. One afternoon, she takes her medication and then decides to drive to pick up her children from school. While driving, she feels unusually sluggish and momentarily drifts into another lane, nearly causing a collision. Another driver reports her erratic driving, and when pulled over, Sarah admits to taking her medication. Although she has no alcohol in her system, a drug recognition expert determines her driving ability is significantly impaired by the medication.
  Explanation: This example demonstrates that a DUI can result from impairment caused by legal prescription drugs. Even without alcohol, Sarah's driving was unsafe due to the medication's side effects, fulfilling the criteria for a Driving Under the Influence charge.
• Scenario: David smokes marijuana with friends at a park and then gets into his car to drive to a nearby convenience store. While driving, he exhibits slow reaction times, fails to stop completely at a stop sign, and makes an unusually wide turn. A police officer, observing these behaviors, pulls David over. The officer notices a strong odor of marijuana and David's dilated pupils. David admits to recent marijuana use, and a subsequent drug test confirms the presence of the substance in his system, indicating impairment.
  Explanation: Here, David is charged with DUI because his driving ability was impaired by an illegal drug (marijuana). His observable driving behaviors and the presence of the substance confirm that he was operating a vehicle while under the influence.