Police officers utilize two primary ways to charge you with "drunk" driving. These are "impaired driving" and "driving with an unlawful blood alcohol level" or "per se" DUI-DWI. These two types of offenses cover over 95% of all active DUI-DWI cases. The remaining cases involve "drugged" driving or impaired driving caused by other substances such as noxious vapors.
Impaired Driving: Most Common DUI-DWI Charge
Impaired Driving is the first and most common type of DUI-DWI. This form of DUI-DWI has the usual components of a traditional (common law) drunk driving case involving these elements (essential parts of the crime that must be proven by the prosecutor to justify a conviction): (a) operating or being in actual physical control of a "vehicle;" (b) on a roadway, public way or other place prohibited by that state's laws (some states cover "any place within the state"); (c) while under the influence of an intoxicating beverage, substance, vapor or chemical, or some combination of these chemicals and substances.
Impaired Driving: The DUI-DWI that Requires Proof of Impairment
This type of DUI-DWI requires proof of impairment through testimony of one or more witnesses, and (where available) a quantitative breath or blood test result for alcohol content. Only Virginia and Nevada have passed legislation establishing presumptive impairment levels based on certain contraband drugs. (Nevada's law was enacted in 2003, while Virginia passed their new law in 2005.)
Impaired Driving: The DUI-DWI that Requires NO Proof of Impairment
A second major type of offense now exists that has absolutely NO REQUIREMENT OF PROVING IMPAIRMENT of the driver. It is sometimes called "Driving UBAL" or "driving with an unlawful blood alcohol level" when the driver has consumed enough alcohol to exceed the applicable legal limit for the driver's age group and vehicle type.
BAC - Blood Alcohol Content Levels
Presently, as a result of legal history, every state in America has very similar laws covering these various situations: Drivers age 21 and over, in a non-commercial vehicle - 0.08%, Drivers under age 21 [ZERO TOLERANCE**] - > 0.00 to 0.02%, Any driver of a commercial motor vehicle - 0.04%. (** State laws vary from a 0.00%, 0.01% or 0.02% standard for "zero tolerance." Go on-line to review your state's law for underage drivers: http://www.theduibook.stateDUIDWIsummaries.htm.)
For those who take the state's test and render a sample with an alcohol level at or over the state's legal limit, this alone (assuming the test result gets into evidence and is believed by the jury or judge hearing your case) constitutes the separate offense of DUI-DWI "per se").
DUI-DWI Involving Contraband Drugs and Impairment Levels
Quantitative impaired driving limits for contraband drugs have not YET been "established" by the federal government, but that this legislation will be enacted within the next 2 to 5 years. Hence, today, only ALCOHOL has quantitative impairment guidelines limits for traditional DUI-DWI.