There is a national effort to crack down on underage DUI and it is a policy which the public overwhelmingly supports. Zero tolerance policies mean it is illegal for anyone under age 21 to operate a motor vehicle with any amount of alcohol in his system. In most states, DUI charges do not require a certain percent of B.A.C. for an underage driver; rather even the slightest amount of alcohol can result in a conviction.
Harsh penalties are common for underage DUI. For example, in Arizona, minors who are found guilty of underage DUI in Tempe may get up to 6 months in jail. A jail sentence is not mandatory, but anyone convicted will have at least a class one misdemeanor conviction on his record which will have a detrimental effect future employment opportunities, college entrance opportunities, and car insurance rates. The court can suspend the minor's driver's license for up to two years; impose fines and surcharges totaling thousands of dollars. The court can also order you to perform community service.
Rather than going easy on drivers who are young, the court is more likely to treat these offenses harshly in the hope that the court can prevent future problems for the driver who does not take drinking and driving seriously at a young age. You need to take the charges very seriously and you need experienced legal representation to defend you against possible harsh penalties.
In addition to the charge of Underage DUI, you may also be charged with regular DUI charges. If your blood alcohol concentration is above .08, you can be charged for both Underage DUI and a regular DUI. The mandatory penalties (including jail time) apply to minors under age 21.