DEFINITIONS:
"Per Se" Blood Alcohol Concentration (BAC) Level
As of August 2005, all states have DUI laws that deem "per se intoxicated" any driver with a blood-alcohol concentration (BAC) at or above .08 percent. This means that drivers with a BAC at or above .08 are intoxicated in the eyes of the law, and no additional proof of driving impairment is necessary.
"Zero Tolerance" Blood Alcohol Concentration (BAC) Level
All states carry "zero tolerance" laws that target drivers under the legal drinking age. These laws penalize persons under 21 for operating a vehicle with any trace of alcohol in their systems (a BAC above 0.0), or with negligible BAC levels such as .01 or .02 percent.

"Enhanced Penalty" Blood Alcohol Concentration (BAC) Level
Many states impose harsher penalties on DUI offenders with a particularly high BAC at the time of the offense, typically .15 to .20 percent. DUI offenders with a BAC at or above their state's enhanced penalty standards will likely face additional jail time, harsher fines, and more severe driver's license sanctions.

"Implied Consent" Laws
"Implied consent" laws require vehicle drivers to submit to some form of chemical test, such as breath, blood, or urine testing, if suspected of DUI. If a driver refuses to submit to such testing, implied consent laws carry penalties such as mandatory suspension of a driver's license, usually for six months to a year.