Just about everyone’s got a DUI story these days, and there seem to be as many contradictory rules around drunk driving as there are tales of woe. The fact is that many jurisdictions define driving under the influence differently. Even so, there are many common elements and overlapping definitions. Here’s a broad overview of how DUI is defined and what authorities must generally prove to get a DUI conviction.

Definition of Drunk Driving

Most state laws define crimes of drunk driving as driving a motor vehicle on a road or highway while under the influence of alcohol. This can mean that you have driven poorly, even if your blood-alcohol concentration (BAC) is low. Newer statutes also provide for what is called a “per se offense,” which a person commits when driving a motor vehicle on a road or highway with a blood-alcohol concentration of .08 percent. This means that even if you have driven perfectly, you can still be charged with driving under the influence.

The “Driving” Element of DUI Laws

Several state statutes require a person to be driving a vehicle in order to be convicted of a drunk driving offense. Other states use the terms “operating a vehicle” or “being in actual physical control of the vehicle.” These terms are not normally synonymous, so it is important to determine how an individual state defines the term in its laws.

A number of questions may arise that relate to the "driving" element of a drunk driving offense. For instance, a person may be in a car without turning on the ignition. The question in some cases is whether the person was driving or operating a vehicle or whether the person was using the vehicle as a temporary shelter. Courts in various jurisdictions have identified several factors that may be used to determine whether someone has been driving a vehicle. These are generally:

• The location of the vehicle (on or off roadway);
• The location of the driver (where in the vehicle);
• The location of the keys in the vehicle (in or out of the ignition); and
• The operability of the vehicle (could the vehicle be driven).

The “Under the Influence” Element of DUI Laws

Officers generally use three types of evidence to determine whether a driver was under the influence: field evidence, driver evidence, and blood-alcohol evidence. Field evidence is normally collected by police officers and may fall into one of five categories:

• Testimony regarding the driver’s unusual driving;
• Testimony regarding the driver’s conduct or physical appearance;
• Testimony regarding the defendant's performance during a field sobriety test;
• Tapes, film, and/or photographs taken at the scene where the defendant was driving and/or arrested; and
• Incriminating statements made by the driver.

Police officers will often look at the driver’s physical appearance and symptoms of drunk driving in order to determine if there is evidence that the driver is intoxicated. The following are some of the more common symptoms of intoxication:

• The defendant's clothes are disheveled;
• The defendant has not shaved or combed his or her hair;
• The defendant's eyes appear to be red, glassy, or bloodshot;
• The defendant's face appears to be flushed;
• The defendant's breath smells like alcohol; or
• The defendant's speech is thick and slurred.

Finally, the defendant's BAC level can be determined through one of three methods. The most common of these methods involves an analysis of the defendant's breath. Other tests analyze the blood or urine of the defendant. Refinements in the methods by which a defendant's BAC is determined have strengthened the ability of prosecutors to prove this BAC. However, these tests are not above reproach, and skilled defense attorneys may be able to successfully attack the methods by which the defendant's BAC was analyzed. While a driver can refuse certain BAC tests, there can be serious penalties for refusal.

Don't Delay: Get Legal Help With Your DUI Today

The elements of a DUI offense can be difficult to figure out if you're not a legal professional. Before pleading guilty, it may be worth your while to see whether the prosecution is actually able to prove these elements. If you've been arrested or charged with DUI, you'll likely benefit from the assistance of an experienced DUI attorney.