Driving under the influence is known as DUI. It is a law that forbids driving motor vehicles while drunk. Any person who drives a vehicle with .8%-.10% alcohol concentration in his blood level is likely to be charged with DUI. Driving while intoxicated (DWI) and operating while intoxicated (OWI) are the other terms used to describe driving under the influence. DUI includes drugs as well as alcohol. The suspicion of driving while under the influence of drugs may be proper grounds for a charge of DUI. If the law enforcement officer suspects a person driving under the influence after the person stops (based on smell of alcohol or drugs etc.) the person can be arrested for DUI.

When a police officer pulls a car over on suspicion of DUI, he may ask for ordinary credentials, including license and registration. The officer may ask the person to step out of the car and perform one of several field sobriety tests (FSTs). These are quick exercises for the driver, intended to indicate whether or not he/she is intoxicated. Even if an FST is not performed, the officer is likely to perform a chemical test, which more accurately indicates sobriety or insobriety. A breathalyzer may be used at the initial traffic stop, or the suspect may be taken back to the station for a blood or urine test.

A DUI suspect is usually given the choice of which chemical test he wants to take among the various options. Many people think that it might baffle the judicial system if the person refuses to take the chemical test. Most states have established provisions with penalties for DUI suspects that fail to take a chemical test--penalties that can be much stricter than those for the ordinary offenders.

If the person is convicted for DUI then the penalties vary from state to state, and largely depend on the circumstances of the offense. Suspension/revocation of license, fine, and imprisonment, and minimum sentences for a first, second or third convictions are some of the means of penalizing DUI offenders.