Underage DUI: Zero Tolerance Laws

It is illegal for people under the age of 21 to purchase and possess alcohol in all 50 states plus the District of Columbia. And while driving under the influence of alcohol (0.08 percent or higher blood-alcohol concentration) is illegal for all motorists, all states have so-called "zero-tolerance" laws for underage DUI offenses.

Zero-tolerance laws make it a criminal DUI offense for motorists under the age of 21 to drive with even a negligible amount of alcohol in their system, ranging from 0.00 to 0.02 percent BAC (depending on the state).

In light of such laws, even an innocent glass of wine with dinner could saddle a young motorist with a DUI charge. But the intent of these laws is to combat the very real dangers of underage drinking.

Nearly one-third of all deaths of 15- to 20-year-olds are the result of a motor vehicle crash and about 35 percent of those fatalities are alcohol-related, according to the National Highway Traffic Safety Administration. The alcohol involvement rate for young drivers is roughly twice that of over-21 drivers, according to the NHTSA, while underage drinking at even low levels presents a greater risk of fatal crashes.

The National Highway Systems Designation Act of 1995 mandated that states consider a 0.02 percent BAC (or lower) for under-21 drivers to be driving under the influence in order to qualify for Federal-Aid Highway Funds. To comply, as all states eventually have, they had to set 0.02 percent BAC as a per se offense. That means police don't have to prove intoxication as long as the driver is above the stated limit.

Beyond the obvious risks to health and safety posed by underage drinking and driving, DUI offenses can have long ranging implications which reach far into a young driver's future.

Visit FindLaw's overview of state DUI laws to find out the per se BAC limit for under-21 motorists in your state.