As many drivers in Arizona will know, being charged with drunk driving is a very serious matter. In general, the legal limit is 0.08 percent. If your blood alcohol concentration is under this number, then the chances are that you will not be charged. However, this is only the case if you are aged 21 or over. Any younger than that and you are below the legal drinking age.

The problem with this is that even though you may not be drunk, you are still considered to be in breach of the law. As a result, each state has limits in place known as zero-tolerance laws. These dictate a separate BAC limit for under-21s. However, this varies from state to state, ranging from 0.02 percent, a quarter of the normal limit, to as low as 0.00.

Of course, in states where the limit is zero, this means that any alcohol found in your system when you are driving could result in a DUI charge. As this article on underage drinking explains, the reason behind this is that alcohol-related motor accidents account for a large proportion of deaths of youths aged 15 to 20.

However, the harshness of these rules can mean that a young person can unwittingly put themselves over the limit with a single drink. Soon they may have a criminal record, restricted access to housing and less chance of getting the college place they wanted. If you are facing DUI charges, you might benefit from the advice of an attorney. He or she can weigh up the details of your situation and may be able to assist you with forming your defense.