In a commentary about drunk driving, dated November 6, 1998, the National Highway Traffic Safety Administration, Department of Transportation and the U.S. Department of Labor discussed DUI/DWI laws and penalties. They said that all but 2 states (Massachusetts and South Carolina) and the District of Columbia have per se laws defining it as a crime to drive with a blood alcohol concentration (BAC) at or above a proscribed level, usually 0.10 percent. Fourteen states mandate jail or community service after first convictions. License suspension or another penalty may result from violations of BAC thresholds that apply only to young drivers in 44 jurisdictions. These underage BAC laws apply to drivers younger than 21 except in Georgia, Louisiana, Vermont (younger than 18 in these states), and Wisconsin (younger than 19).
License suspension or revocation traditionally follows conviction for alcohol-impaired driving. Under a procedure called administrative license suspension, licenses are taken before conviction when a driver fails or refuses to take a chemical test. Because administrative license suspension laws are independent of criminal procedures and are invoked right after arrest, they've been found to be more effective than traditional post-conviction sanctions. Forty states and the District of Columbia have administrative license suspension laws.
Per se law
In most states, the first offense is a misdemeanor which carries penalties and punishment that have both immediate and long term consequences. Many states have set limits on how much alcohol a person can have in his or her system in order to be deemed in violation of the law. These "not to exceed levels" are called "per se" laws.
The per se limit in almost all states is either .08 or .10. This means that you are presumed to be under the influence if you are above the mandated level. However, the blood-alcohol level is only one of many factors to be considered in the defense of a drunk driving charge.
Legal limits in your state
Courtesy of the National Highway Traffic Safety Administration, Department of Transportation, US Department of Labor. Last Updated: November 6, 1998.


