the act of operating a motor vehicle after having consumed alcohol or
other drugs, to the degree that mental and motor skills are impaired.
All 50 states now have two statutory offenses. The first is the
traditional offense, variously called driving under the influence of
alcohol (DUI), driving while intoxicated/impaired (DWI) or operating while intoxicated/impaired (OWI). The second and more
recent is the so-called illegal per se offense of driving with a
blood-alcohol concentration (BAC) of 0.08% (previously 0.10%) or higher.
The first offense requires proof of intoxication, although evidence of
BAC is admissible as presumptive evidence of that intoxication; the
second requires only proof of BAC at the time of being in physical
control of a motor vehicle. An accused may be convicted of both
offenses, but may only be punished for one. It is also a criminal
offense in all states to drive a vehicle while under the influence of
drugs DUID, or under the combined influence of alcohol and drugs; the
drugs themselves need not be illegal, but can be prescription or even
over-the-counter. This offense requires evidence of impairment as a
result of the drugs or drugs and alcohol. All states also now have zero
tolerance laws: the license of anyone under 21 driving with a BAC of
.01% or higher (.02% in some states) will be suspended. The
blood-alcohol limit for commercial drivers 0.04%.