Some people use their state's blood alcohol limit as a guideline for driving while intoxicated. Any DWI attorney will tell you that that is not what is meant by "over the legal limit" or "under the legal limit." Here is why you were still arrested for a DWI when you used blood alcohol levels as a driving guideline.
Driving After Drinking Is Illegal, Period
Driving after having a drink or having ten drinks is illegal, period. Most states establish a blood alcohol level as a means of determining how much danger an intoxicated driver is in or in how much danger he/she will put others. Driving while intoxicated on one drink is really no better than driving drop-down drunk in most legal eyes because you still chose to get behind the wheel of a car with alcohol in your system.
The Police Can Fine You "Under the Limit" and Arrest You for "Over the Limit"
Blood alcohol levels are established in order for law officers to determine how to best punish you for drinking and driving. The whole "under the legal limit" thing is so that you are not arrested and jailed for drinking a little. Jailing you for "under the limit" is extreme punishment and is often considered "cruel and unusual punishment" under the law, which is why these blood alcohol limits were created. Drinking until you are "over the legal limit" gives officers permission to remove you from the road, fine you, and jail you for endangering yourself and others. In these instances, you could have injured or killed yourself or others because your blood alcohol levels were too high, and jailing you is appropriate punishment for deterring such behavior and/or poor decisions.
If You Were "the Least Drunk," That Is No Excuse
When friends go out drinking together, they often decide who drives by suspected blood alcohol level or who seems "the least drunk." This is still a bad guideline for driving and is really no guideline at all. If you are pulled over and you have the least amount of alcohol in your system, you will still be fined even though you have the least blood alcohol level of everyone in the vehicle. The police officer will not look at your friends and tell you you made a good call or take the blood alcohol levels of everyone in the car for a comparison and let you go. More than likely, you will have to get other transportation, pay a fine, appear in court, and/or hire a DWI attorney to get you out of trouble.